WO2012129755A1 - Imaging array unit using ultra-violet avalanche photo diodes, application method thereof, and imaging array composed of the same - Google Patents

Abstract

An imaging array unit using ultra-violet avalanche photo diodes, an application method thereof, and an imaging array composed of the same. The imaging array unit (300) consists of a plurality of avalanche diode detectors (200-1∼200-3) connected in parallel, wherein the avalanche diode detectors consist of photo diodes, thin-film resistors (207-1∼207-3), and a metal layer (210) connected in series. In each of the avalanche diode detectors, the n-type semiconductor (202) of the photo diode is electrically connected to a contact electrode (203-1, 203-2), and the contact electrode provided in each avalanche diode detector of the imaging array unit is electrically connected with one another and used as one electrode. All the avalanche diode detectors share a complete metal layer, the other electrode of the imaging array unit. The imaging array is composed of a plurality of imaging array units. The imaging array unit using ultra-violet avalanche photo diodes, of a new structure, overcomes the problem of lower yield caused by the high defect density in the material itself, which enables the yield to approach or even reach 100%.

Description

 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet avalanche tube imaging array pixel, an application method thereof, and an avalanche tube imaging array. BACKGROUND OF THE INVENTION The detection of ultraviolet light, especially in the solar blind, has extremely important applications in space detection and military applications. At present, the photon counting system in the ultraviolet band uses a photomultiplier tube (PMT), but the photomultiplier tube is bulky, fragile, high in operating voltage and expensive, so a small-sized, inexpensive solid-state ultraviolet detector is very important. The advantages.

In recent years, with the advancement of GaN and AlGaN materials, reports of UV avalanche tubes and single photon detection avalanche tubes (SPAD) of GaN-based and AlGaN-based materials have also appeared in the laboratory. However, due to the lattice misalignment of GaN and AlGaN materials, the defect density in the material is very large (the reported dislocation density of GaN and AlGaN materials is 10 ⁷ cm - ² to 10 1 ^Q cm - ² ), especially in AlGaN materials. As the content of the A1 component increases (the larger the A1 content, the larger the forbidden band width of AlGaN, the shorter the detection cutoff wavelength), the greater the defect density. Therefore, GaN-based and AlGaN-based avalanche tubes and single-photon detection avalanche tubes are very difficult to manufacture. If the defect density of AlGaN materials is 10 ⁸ cm - ² , then according to the yield formula

Y=( ) ² [WAY KUO, FELLOW, IEEE, AND TAEHO KIM, PROCEEDINGS OF THE IEEE,

AD

VOL. 87, NO. 8, AUGUST 1999], (where A is the device area and D is the defect density.) The yield of the AlGaN avalanche tube is extremely low, and the larger the area of the avalanche tube, the lower the yield. Figure 1 is a graph showing the relationship between the yield of the AlGaN avalanche tube and the device area. It can be seen that if the avalanche tube area is ΙΟ ΙΟ ΙΟμηι ² , the yield is less than 1%, assuming a 1KX 1K UV is required. Optical avalanche tube imaging array, in which the number of good quality pixels is only 10Κ, and the remaining 990 pixels are bad. Such an imaging array cannot work at all, so it is difficult to use traditional avalanche tubes at the current yield. The structure implements an ultraviolet avalanche tube imaging array.

As shown in FIG. 2A, the APD 100 is a typical silicon-based metal-resistance-semiconductor (MRS) [V. Saveliev, V. Golovin, Nuclear Instruments and Methods in Physics Research A 442 (2000): 223-229] Structure Avalanche The tube detector, whose basic structure is composed of a photodiode 101, a thin film resistor 102 and a metal electrode 103, the thin film resistor 102 and the p-type semiconductor end of the photodiode 101 are in electrical contact, and then the metal layer 103 is deposited on the thin film resistor 102. It is in contact with the thin film resistor 102, and its equivalent circuit is shown in Fig. 2B. In operation, a negative voltage Vbias is applied to the MRS structure avalanche tube APD 100. When there is no light, the photodiode 101 is in a negative bias state, the diode 101 is equivalent to a capacitor, and the negative voltage Vbias is mainly distributed on the photodiode 101. If a photon reaches the diode 101, the photon is absorbed to generate electron-hole pairs, electrons and holes generate more electrons and holes in the multiplication region, and the photodiode 101 avalanches, so that the optical signal is converted into an electrical signal and amplified. The process can also be seen as a discharge process of a capacitor. At this time, a part of the voltage of the negative bias voltage Vbias is distributed to the thin film resistor 102, so that the voltage applied to the photodiode 101 is lowered, and the avalanche is extinguished, so the thin film resistor 102 has a negative feedback. The role. Once the voltage on photodiode 101 decreases, the avalanche process is extinguished. At this time, the diode 101 is recharged and the voltage is increased to be able to detect the next optical signal.

 As mentioned above, due to the lattice misalignment of GaN and AlGaN materials themselves, the defect density is very large, GaN and AlGaN avalanche tubes are difficult to manufacture, and the yield is extremely low, and the ultraviolet avalanche tube imaging array cannot be realized. SUMMARY OF THE INVENTION The present invention provides an ultraviolet avalanche tube imaging array pixel, which can effectively overcome the defects of the semiconductor material itself and improve the yield.

 The invention also provides an application method of the ultraviolet avalanche tube imaging array pixel and an avalanche tube imaging array composed thereof.

 The ultraviolet avalanche tube imaging array pixel is formed by a plurality of avalanche tube detectors connected in parallel, wherein the avalanche tube detector is sequentially connected by a photodiode, a thin film resistor and a metal layer, and each of the avalanche tube detectors is photoelectrically The n-type semiconductor of the diode is connected to the contact electrode, and the contact electrode of each avalanche tube detector in the imaging pixel forms an electrical connection as an electrode, and each avalanche tube detector shares a complete metal layer, and the metal layer forms an ultraviolet avalanche tube. The other electrode of the imaging array cell.

 More preferably, the ultraviolet avalanche tube imaging array pixel comprises, in order from bottom to top, a plurality of independent photodiodes, an insulating passivation layer, and a plurality of independent thin film resistors and insulating mediums corresponding to the plurality of photodiodes. a layer and a metal layer, wherein the passivation layer is provided with a plurality of first contact holes, so that the p-type semiconductor end of each photodiode is electrically contacted with the corresponding thin film resistor through the first contact hole, and the insulating dielectric layer is provided with a plurality of The second contact hole causes each of the thin film resistors to make electrical contact with the metal layer through the second contact hole.

 As a common general knowledge, both the passivation layer and the dielectric layer are electrically insulating layers. Preferably, the method for preparing the ultraviolet avalanche tube imaging array pixel comprises the following steps:

 (1) sequentially forming an n-type semiconductor and a p-type semiconductor on the substrate;

 (2) etching the p-type semiconductor to form a plurality of independent photodiode structures, and forming a plurality of contact electrodes corresponding to the photodiodes in the n-type semiconductor in the etched region;

 (3) depositing a passivation layer and etching over the photodiode to form a first contact hole;

 (4) depositing and etching to form a thin film resistor, and the thin film resistor is in electrical contact with the corresponding photodiode unit through the first contact hole;

 (5) depositing a dielectric layer and etching over all of the thin film resistors to form a second contact hole;

 (6) Depositing a metal layer and making electrical contact with all of the thin film resistors through the second contact hole.

As shown in FIG. 3B, the basic unit of the ultraviolet avalanche tube imaging array pixel (hereinafter referred to as UV-APD 200) may be the substrate 201 from the bottom up, the n-type semiconductor 202, the n-type contact electrode 203, p-type The semiconductor 204, the n-type and p-type semiconductors are epitaxially formed by MOCVD; then the p-type semiconductor is etched to form n rows of contact electrodes 203; the passivation layer 205 is deposited to form contact holes 206, and a thin film resistor 207 is formed. Forming the thin film resistor 207 and the p-type semiconductor Electrical contact; finally, a dielectric layer 208 is deposited and a contact hole 209 is formed, the metal layer 210 and the thin film resistor 207 form an electrical contact, and 211 is a contact electrode. Where the substrate 201 is a transparent or translucent material, the metal layer 210 may be a transparent or translucent material.

 The ultraviolet avalanche tube imaging array pixel (hereinafter referred to as UV-APD 300) may be formed by a plurality of UV-APDs 200 in parallel, as shown in FIG. 3A, UV-APD 200-1, 200-2, 200-3 are Three UV-APDs 200, which are connected in parallel by a metal layer 210 and a common contact electrode 203-1, 203-2, the basic process of which is illustrated in Figure 3C:

 Step 212, forming an n-type semiconductor 202 and a p-type semiconductor 204 on the substrate 201, and epitaxially growing the semiconductor material by MOCVD;

 Step 213, etching a p-type semiconductor, forming contact electrodes 203-1 and 203-2 on the n-type semiconductor, and the contact electrodes may be connected together by a metal line as a contact electrode;

 Step 214, depositing a passivation layer 205 and etching to form a contact hole 206;

 Step 215, depositing and etching to form thin film resistors 207-1, 207-2 and 207-3;

 Step 216, depositing a dielectric layer 208 and forming a contact hole 209;

 Step 217, depositing a metal layer 210 and making electrical contact with the film resistor, and the metal layer 210 constitutes another electrode 301.

The equivalent circuit diagram of the UV-APD 300 is shown in FIG. 3D. The UV-APD 300 is formed by a plurality of UV-APDs 200 connected in parallel, and the cathodes of all the UV-APDs 200 are connected together by the metal layer 210 to form an electrode, the contact electrode. The 203 are joined together to form another electrode. The UV-APD 300 thus constructed is actually composed of a plurality of UV-APD 200 units connected in parallel. As mentioned above, the yield Y of GaN and AlGaN-based avalanche tubes is very low due to the high defect density of GaN and AlGaN materials. If UV-APD 300 is composed of a suitable number of UV-APDs 200 in parallel, then UV-APD There are always a certain number of good quality UV-APD 200 in 300, so the UV-APD 300 can always detect the optical signal, so the UV avalanche tube imaging array of this structure has a pixel yield close to 100%, which can be realized. Ultraviolet avalanche tube imaging arrays overcome the problems caused by the high defect density of GaN and AlGaN materials themselves.

 The photodiode in the ultraviolet avalanche tube imaging array pixel is made of a m-v family and/or a π-νι group semiconductor material, preferably made of at least one of GaN, AlGaN or A1N.

 The radius of the avalanche tube detector unit in the ultraviolet avalanche tube imaging array pixel is preferably from 1 to 50 μm.

Preferably, the resistance of each individual thin film resistor is from 100 Ω to 10 Ω; the preferred material of the thin film resistor is SiC or Si _x O _y .

Since the defect density of GaN and AlGaN materials is large, the yield of GaN and AlGaN-based avalanche tubes is very low; some UV-APDs 200 are bad in UV-APD 300, so when there is no light plus negative bias, these A bad avalanche has occurred in the UV-APD 200. At this time, there is an electrical signal I _B on the electrode 301. This electrical signal is a dark current. We can call this current the bottom current; and those of good quality UV-APD 200 will work properly. In a specific operation, the application method of the ultraviolet avalanche tube imaging array pixel is: applying a negative bias voltage to the ultraviolet avalanche tube imaging array pixel, so that the ultraviolet avalanche tube imaging array pixel works, when there is no light The measured photo-current of the ultraviolet avalanche tube imaging array is I _B , which is used as the pixel bottom current; when there is light, those good quality UV-APD 200 undergo avalanche process to convert the optical signal into electricity. The signal is amplified and the pixel current of the ultraviolet avalanche tube imaging array is measured. The magnitude of the multiplied current generated by the light is IC=IS-IB, which is the size of the electrical signal obtained by the ultraviolet avalanche tube imaging array pixel.

 Ultraviolet avalanche tube imaging array pixels operate in linear amplification mode or Geiger Mode [D. Renker, Nuclear Instruments and Methods in Physics Research A 567 (2006) 48-56]. The applied negative bias is 10V to 100V.

 The avalanche tube imaging array is composed of a plurality of the ultraviolet avalanche tube imaging array pixels.

Since the UV-APD 300 is obtained by connecting a plurality of UV-APDs 200 in parallel, the area of the UV-APD 200 can be made small, which improves the yield of the UV-APD 200 without affecting the photosensitive area of the UV-APD 300. If the UV-APD 300 is composed of a suitable number of UV-APDs 200 in parallel, there is always a certain number of good quality UV-APDs 200 in the UV-APD 300. If the defect density of GaN is 10 ⁷ cm - ² and the area of UV-APD200 is 5χ5μηι ² , the yield of UV-APD200 is 13% according to the yield formula, if the UV-APD 300 is composed of 10x10 UV-APD 200 units. The composition, the UV-APD 200 in the pixel UV-APD 300 is of good quality, so that the UV-APD 300 can always detect the optical signal, so the purple ultraviolet avalanche tube imaging array of this structure is good. The rate is close to 100%, which overcomes the problems caused by the high defect density of GaN and AlGaN materials themselves. As shown in FIG. 4, the UV-APD 300 is composed of 16 UV-APDs 200 in parallel. If there is always a good quality UV-APD 200 in the pixel, the UV-APD 300 is a good quality image pixel, which can The optical signal is detected and the yield is nearly 100%, and the ultraviolet avalanche tube imaging array can be realized.

 As a result of the foregoing analysis, the yield of the ultraviolet avalanche tube imaging array pixel UV-APD 300 of the present invention is close to 100%, so that the avalanche tube imaging array can be fabricated by using the UV-APD 300 as an imaging unit. As shown in FIG. 5, the UV-APD ARRAY 500 is an avalanche tube imaging array composed of NXN UV-APD 300. It is mentioned above that since the yield of the pixel UV-APD 300 is close to 100%, the imaging array UV- In the APD ARRAY 500, all the pixel units are of good quality, so the ultraviolet avalanche tube imaging array pixel UV-APD 300 of the present invention overcomes the inability to achieve ultraviolet light due to the high defect density of the GaN and AlGaN materials themselves. Avalanche tube imaging array problems.

At the same time, the novel structure proposed by the present invention can also be used to fabricate a large photosensitive area ultraviolet avalanche tube imaging array pixel. Since the defect density of the GaN and AlGaN materials themselves is relatively large, a large-area ultraviolet avalanche tube is very difficult to manufacture, but In the present invention, the UV-APD 300 is composed of a plurality of UV-APDs 200 in parallel, which can make the area of the UV-APD 200 small, improve the yield of the UV-APD 200, and is composed of a plurality of UV-APDs 200. UV-APD 300 increases the photosensitive area without affecting the yield. For example, we need to make a UV avalanche tube imaging array pixel of the size of ΙΟΟ ΙΟΟ ημηι ^2. If the conventional structure is used, the yield is less than 1%. If the invention is used, if the area of the UV-APD 200 is 5χ5μηι ² ( As the process progresses, the size can be made smaller.) The yield of UV-APD 200 is about 10%, then 20-20 UV-APD 200 can be used to form UV-APD 300, so that the pixel area reaches 100 X ΙΟΟμηι ² , and its yield can be close to 100%, which is not possible with the current avalanche tube structure. If the development of material technology causes the defect density of materials such as AlGaN and GaN to be reduced, then the same 50 Χ 50μηι ² size ultraviolet avalanche tube imaging array pixel, the yield of the conventional structure and the ultraviolet avalanche tube imaging array image of the present invention are produced. The relationship between the yield of the element and the defect density is shown in Fig. 6 (the UV avalanche tube imaging array of the present invention is composed of 10 x 10 5 χ 5 μη ² sized UV-APD 200 cells), and it can be found only when AlGaN and GaN materials are used. When the defect density is reduced to 10 ⁴ cm ^-2 , the yield of the conventional structured ultraviolet avalanche tube can be compared with the present invention. Therefore, by using the ultraviolet avalanche tube imaging array pixel structure proposed by the present invention, a large photosensitive area can be made. The UV avalanche tube cell avoids the problem of a drop in yield due to the large area.

 The effective effects of the present invention are:

 The ultraviolet avalanche tube imaging array pixel structure of the invention overcomes the problem that the defect density of the multi-defective material such as GaN, AlGaN and the like is too high, and the yield of the novel structure ultraviolet avalanche tube imaging array can be improved. Approaching and reaching 100%, using the ultraviolet avalanche tube imaging array pixel as an imaging unit, an ultraviolet avalanche tube imaging array can be fabricated. In the present invention, the ultraviolet avalanche tube imaging array pixel structure overcomes the problem of low yield of a large area avalanche tube, and the ultraviolet avalanche tube imaging array pixel can be composed of tens or hundreds of smaller basic unit structures UV- The APD 200 is composed, so that a large a photosensitive area of the ultraviolet avalanche tube imaging array pixel can be made, and there is no problem that the yield is lowered because the area is too large. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the relationship between the yield of a conventional avalanche tube detector and the device area of a conventional AlGaN material; FIG. 2A is a schematic view showing the structure of a typical silicon-based MRS avalanche tube detector;

 2B is an equivalent circuit diagram of the silicon-based MRS structure avalanche tube detector described in FIG. 1A;

 3A is a schematic structural view of an ultraviolet avalanche tube imaging array pixel according to the present invention;

 3B is a schematic structural diagram of a basic constituent unit in the ultraviolet avalanche tube imaging array pixel of FIG. 3A;

 3C is a basic process of the ultraviolet avalanche tube imaging array pixel of FIG. 3A;

 3D is an equivalent circuit diagram of the ultraviolet avalanche tube imaging array pixel of FIG. 3A;

 4 is a schematic structural view of a specific ultraviolet avalanche tube imaging array pixel according to the present invention;

 Figure 5 is an avalanche tube imaging array of the present invention;

Figure 6 is a graph comparing the yield of a conventional structured avalanche tube detector with an area of 50 Χ 50 μηι ^{2 and} the yield of the ultraviolet avalanche tube imaging array of the present invention. DETAILED DESCRIPTION OF THE INVENTION A schematic view of an ultraviolet avalanche tube imaging array pixel of the present invention is shown in FIG. If the ultraviolet avalanche tube imaging array pixel UV-APD 300 is composed of a plurality of basic units UV-APD 200 (as shown in FIG. 3A), the radius of the UV-APD 200 may be Ιμηι to 50μηι. In FIG. 3A, we can form the substrate 201 from bottom to top. The substrate 201 can be a material such as SiC, sapphire, or silicon substrate, but requires the substrate to transmit light; the n-type semiconductor 202 and the p-type semiconductor 204, the material can be It is a material such as GaN, A1N or AlGaN. The n-type semiconductor 202 and the p-type semiconductor 204 can be epitaxially grown by MOCVD, and a buffer layer is also formed, thereby reducing lattice dislocations in the material and reducing the defect density; and then etching p The semiconductor is exposed to a portion of the n-type semiconductor, and then the n-type contact electrode 203 is formed. The electrode may be made of a material such as a Ti/Au alloy; the insulating passivation layer 205 is deposited and a contact hole 206 is formed, and the passivation layer may be made of an oxide or the like; Forming the thin film resistor 207 to make the thin film resistor 207 and the p-type semiconductor form electrical contact, the thin film resistor 207 may be made of a material such as SiC or Si _x O _y having a resistance value of about several hundred Ω Ω to 1 Μ Ω; a dielectric layer 208 is deposited and a contact hole 209 is formed, the metal layer 210 and the thin film resistor 207 are in electrical contact, and 211 is a contact electrode.

The ultraviolet avalanche tube imaging array pixel UV-APD 300 of the present invention can be composed of tens to hundreds of UV-APD 200s, and if it constitutes an ultraviolet avalanche tube imaging array pixel of the size ΙΟΟ ΙΟΟ ΙΟΟμηι ² , 20 X can be used. 20 UV-APD 200s with an area of 5 X 5 μm ² are formed, and the process flow is shown in FIG. 3C.

 The simple process flow is:

 An n-type semiconductor 202 and a p-type semiconductor 204 are formed on the substrate 201, and a semiconductor material such as GaN, A1N or AlGaN can be epitaxially grown by MOCVD;

The p-type semiconductor 204 is etched to form a plurality of photodiode array structures having an array size of 20 X 20 and a photodiode having an area of 5 Χ 5 μηι ² .

 Then, a contact electrode 203 is formed on the n-type semiconductor 202, and all of the n-type contact electrodes 203 may be connected together by a metal line as an electrode of the ultraviolet avalanche photoimageable array pixel;

 Depositing an insulating passivation layer 205 and etching over the photodiode unit to form a contact hole 206;

 Depositing and etching to form 20 X 20 thin film resistors 207, and the thin film resistors make electrical contact with the corresponding photodiode cells through the contact holes;

 Depositing dielectric layer 208 and etching over all of the thin film resistors 207 to form contact holes 209;

 The metal layer 210 is deposited and electrically contacted with all of the thin film resistors 207 through the contact holes 209, and the metal layer 210 constitutes the other electrode 211.

The foregoing describes a 100 X ΙΟΟμηι ² size ultraviolet avalanche tube imaging array pixel UV-APD 300. In specific operation, a negative bias voltage Vbias is applied to the electrode 301, so that the pixel UV-APD 300 operates in linear amplification mode or Geiger Mode. The voltage can range from 10V to 100V. The operating voltage varies according to different doping concentrations and process parameters. When there is no light, the current of the pixel UV-APD 300 measured on the electrode 301 is I _B , which is the background current of the ultraviolet avalanche tube imaging array pixel UV-APD 300; when there is light, on the electrode 301 When the current of the avalanche tube is measured as I _s , the magnitude of the current converted by the optical signal is:

IC=IS-IB

That is, I _c is the size of the electrical signal read by the avalanche tube cell UV-APD 300.

Claims

Claim An ultraviolet avalanche tube imaging array pixel, characterized in that a plurality of avalanche tube detectors are connected in parallel, and the avalanche tube detector is formed by sequentially connecting photodiodes, thin film resistors and metal layers, each avalanche In the tube detector, the n-type semiconductor of the photodiode is connected to the contact electrode, and the contact electrode of each avalanche tube detector in the imaging pixel forms an electrical connection as an electrode, and each avalanche tube detector shares a complete metal layer, metal The layer forms the other electrode of the UV avalanche tube imaging array pixel.  2. The ultraviolet avalanche tube imaging array pixel according to claim 1, wherein the ultraviolet avalanche tube imaging array pixel comprises a plurality of independent photodiodes, a passivation layer, and more in order from bottom to top. a plurality of thin film resistors, a dielectric layer and a metal layer respectively corresponding to the photodiodes, wherein the passivation layer is provided with a plurality of first contact holes, so that the p-type semiconductor end of each photodiode and the corresponding thin film resistor pass through A contact hole forms an electrical contact, and a plurality of second contact holes are disposed in the dielectric layer such that each of the thin film resistors makes electrical contact with the metal layer through the second contact hole.  3. The ultraviolet avalanche tube imaging array pixel according to claim 2, wherein the method for preparing the ultraviolet avalanche tube imaging array pixel comprises the following steps:  (1) sequentially forming an n-type semiconductor and a p-type semiconductor on the substrate;  (2) etching the p-type semiconductor to form a plurality of independent photodiode structures, and forming a plurality of contact electrodes corresponding to the photodiodes in the n-type semiconductor in the etched region;  (3) depositing a passivation layer and etching over the photodiode to form a first contact hole;  (4) depositing and etching to form a thin film resistor, and the thin film resistor is in electrical contact with the corresponding photodiode unit through the first contact hole;  (5) depositing a dielectric layer and etching over all of the thin film resistors to form a second contact hole;  (6) Depositing a metal layer and making electrical contact with all of the thin film resistors through the second contact hole.  The ultraviolet avalanche tube imaging array pixel according to any one of claims 1 to 3, wherein the photodiode is made of at least one of GaN, AlGaN or AlN.  The ultraviolet avalanche tube imaging array pixel according to any one of claims 1 to 3, wherein the avalanche tube detector unit in the imaging array unit has a radius of 1 to 50 μm. The ultraviolet avalanche tube imaging array pixel according to any one of claims 1 to 3, wherein each of the individual thin film resistors has a resistance of 100 Ω to 10 Ω, and preferably the material of the thin film resistor is SiC or Si _x O _y . The method for applying the ultraviolet avalanche tube imaging array pixel according to any one of claims 1 to 6, wherein a negative bias is applied to the ultraviolet avalanche tube imaging array pixel to make ultraviolet light Avalanche tube imaging array pixel work, when there is no light, the measured photocell current of the ultraviolet avalanche tube imaging array is I _B , which is used as the pixel bottom current; when there is light, the ultraviolet avalanche tube imaging array pixel is measured. When the current is, the magnitude of the doubling current generated by the light is I _c =I _s - , which is the magnitude of the electrical signal obtained by the ultraviolet avalanche tube imaging array pixel. 8. The method of applying an ultraviolet avalanche tube imaging array pixel according to claim 7, wherein the ultraviolet avalanche tube imaging array pixel operates in a linear amplification mode or a Geiger mode.  9. A method of applying an ultraviolet avalanche tube imaging array pixel according to claim 7 or 8, wherein the applied negative bias voltage is from 10V to 100V.  An avalanche tube imaging array comprising a plurality of ultraviolet avalanche tube imaging array pixels according to any one of claims 1-7.