CN107248517A - The pole detectors of biasing control two waveband InAlAs InGaAs bis- and focal plane arrays (FPA) - Google Patents

Abstract

The invention discloses a bias control dual-band InAlAs-InGaAs diode detector and a focal plane array, belonging to the field of semiconductor optoelectronic information materials and devices. On the same InP substrate, use lattice-matched wide bandgap In _0.52 Al _0.48 As and narrow bandgap In _0.53 Ga _0.47 As ternary materials as short-wavelength and long-wavelength light-absorbing materials, respectively, to build a two-electrode photodetector by stacking Or focal plane array device, the monolithic diode device adopts positive bias or negative bias electric control method to make it produce corresponding short-wave or long-wave response. Since this dual-band photodetector adopts a monolithic stack structure and only has two electrodes, it does not increase the process difficulty compared with single-band devices, and the packaging and readout circuits of single-band devices can still be used after forming a focal plane array device In this form, only the corresponding working band can be selected by switching the bias voltage, which has advantages in application and can be extended to other material systems and working bands.

Description

Bias-controlled dual-band InAlAs-InGaAs diode detector and focal plane array

technical field

The invention belongs to the technical field of semiconductor optoelectronic devices and spectral remote sensing, and in particular relates to a bias control dual-band InAlAs-InGaAs diode detector and a focal plane array.

Background technique

Semiconductor photodetectors (PDs) and their focal plane arrays (FPAs) have important applications in many fields. Conventional PDs or FPAs only target a continuous response wavelength range, but some special applications often need to choose to detect different discrete wavelength ranges. The conventional solution is to use multiple PDs or FPAs to respond to different wavelength bands respectively, but this brings A series of problems such as the complexity of the optical system make it even difficult to achieve the required functions in some occasions.

In order to solve this problem, people have also developed a PD called dual-band (or multi-band, and dual-band is used as an example below). Superimposed combination, for example, two short-wave and long-wave detectors are superimposed in the same shell at the same time. The photosensitive surface of the short-wave detector is a pass-through type (the back is not blocked by electrodes, etc.) and has a large area, and it is placed next to the long-wave detector. In this way, the incident light is first irradiated on the short-wave detector for short-wave detection, and the long-wave light that can pass through the short-wave detector continues to act on the long-wave detector for long-wave detection, and the electrodes of the two detectors are independently drawn out. Requires 3 electrodes (can have a common electrode). The advantage of this form is that the two detectors are completely independent and can output at the same time. The disadvantage is that the packaging process is complicated and the size is large, which is difficult to use in FPA. 2) Directly grow the independent structures of the two waveband detectors vertically on the same substrate by means of epitaxy, and then still use microelectronics methods to fabricate devices. When this kind of dual-band detector works, the incident light first passes through its upper structure to generate a short-wave response, and the remaining light continues to pass through the lower structure to generate a long-wave response. This type of device can also be fabricated by bonding, etc. The advantage of this form is that the two detectors can still be completely independent and output at the same time. The disadvantage is that the two detectors still need to lead out electrodes independently (there may be a common electrode), so at least 3 electrodes are still required, and the micro It will be difficult to lead out the intermediate electrode in electronic processing. Although this form can be used in FPA in principle, it is difficult to arrange the design and processing of the readout circuit for the two detection band electrodes of each unit, which limits its development. 3) If the short-wave and long-wave structures are vertically integrated and connected in series through tunnel junctions, etc. to form a diode device in the form of a multi-junction photovoltaic cell, these junctions cannot produce photovoltaic effects at the same time under the action of a single short-wave or long-wave light. , that is, the non-responsive structure limits the output of the responsive structure, so it cannot be used as a dual-band device. Although the pinning effect of such a device can be eliminated by applying optical bias, so as to realize the dual-band detection function, the introduction of the optical bias system will also significantly increase the complexity of the system.

In addition, different from the above three forms, for dual-band and multi-band detectors and focal plane detectors, different detection bands can be formed by splitting light through optical systems, using longitudinal Bragg gratings or transverse planar gratings, or forming resonance structures, etc. Many ways. The above discussion of dual-band devices can also be extended to multi-band devices, which will not be repeated here. For conventional photodetectors, it is determined by the principle that its response on the short-wave side is not cut-off but just keeps falling, so there are also various detectors that enhance short-wave response, but the response band of this device is still continuous and single , for so-called dual-band detection still needs to use optical splitting or filtering system, which is not included in the discussion of the present invention.

Contents of the invention

The purpose of the present invention is to provide a scheme for fabricating a bias-controlled dual-band InAlAs-InGaAs two-electrode detector and focal plane array integration by a monolithic vertical integration method.

The scheme of the present invention is similar to the above-mentioned form 2, and still use the epitaxial method to directly grow two waveband detector structures vertically on the same substrate. In the specific structure, only two kinds of materials (except the substrate material) are involved in the wide bandgap and narrow bandgap. The difference is that the detection structures of the two bands are not completely independent but interrelated; in terms of chip manufacturing, microelectronics methods are still used to make devices in the follow-up process, and the difference is that there is no need to make three or more electrodes for this dual-band detector , and still only need two electrodes like a single-band detector, it is a "diode" device, and it can form a dual-band detection function by electronic control without applying an optical bias like Form 3; When the dual-band detector works, the incident light first passes through the upper structure to generate a short-wave response, and the remaining light continues to pass through the lower structure to generate a long-wave response. Through the selection and optimization of the material system, the two detection bands can be separated and well connected. In this monolithic vertically integrated dual-band dipole detector, the detection structures of the two bands can still be optimized independently, and the signals of the two bands can be output by selecting or time-division multiplexing for specific applications. Since this device does not require an intermediate electrode, the microelectronic processing is still the same as that of a conventional single-band device, and does not increase the difficulty of the process. This kind of dual-band detector form is very suitable for FPA integration, because each detection unit still uses only one readout electrode in addition to the total common electrode, and it can still cooperate well with traditional readout circuits in form. There is no difficulty in circuit interconnection and subsequent packaging.

The gist of the present invention is: for the front light input devices (including unit devices, linear devices, etc., please refer to the left side of the drawing), first use methods such as molecular beam epitaxy (MBE) or metal-organic vapor deposition (MOCVD) on semi-insulating Substrate 1 is sequentially epitaxially grown to match its lattice: n-type highly doped lower contact layer 2, n-type low-doped narrow-bandgap long-wave absorbing layer 4, p-type highly-doped wide-bandgap layer 5, n-type low-gap layer Doping the wide-bandgap short-wave absorbing layer 6 and the n-type highly doped narrow-bandgap upper contact layer 7, and then using microelectronics technology to etch out the mesa, and at the same time, the n-type highly doped lower contact layer 2 and the n-type highly doped The lower contact electrode 3 and the upper contact electrode 8 are formed on the upper contact layer 7, and the same method as that of the single-band device is still used for subsequent processing and packaging.

Similar to this, for backside light input devices (incident light enters from one side of the substrate, including unit devices, line array devices and area array devices, etc., see the right side of the figure), molecular beam epitaxy (MBE) or metal Organic material vapor deposition (MOCVD) and other methods epitaxially grow on the semi-insulating InP substrate 1 to match its lattice: n-type highly doped lower contact layer 2, n-type low-doped wide-bandgap short-wave absorbing layer 6, p-type The highly doped wide bandgap layer 5, the n-type low-doped narrow-bandgap long-wave absorbing layer 4, and the n-type highly doped narrow-bandgap upper contact layer 7 are then etched with a microelectronics process to form a mesa, and at the same time, the n-type The lower contact electrode 3 and the upper contact electrode 8 are fabricated on the n-type highly doped lower contact layer 2 and the n-type highly doped upper contact layer 7, and the subsequent processing and packaging are still carried out in the same way as the single-band device. That is, the order of the three layers 4, 5, and 6 is changed to 6, 5, and 4 compared with the front light input device.

The response band of this device can be conveniently controlled by forward or reverse bias applied to the two electrodes. Take the front light input device as an example: when the following electrode is used as the reference electrode of the PD or the common electrode of the FPA, when a positive bias is applied to the upper electrode, it consists of a p-type highly doped wide bandgap layer 5 and an n-type low-doped The heterogeneous pn junction long-wave detection structure composed of the heterogeneous narrow-bandgap long-wave absorption layer 4 is in a forward biased state and can provide a sufficiently large injection current, while the n-type low-doped wide-bandgap short-wave absorption layer 6 and the p-type highly doped The homogeneous np junction short-wave detection structure formed by the wide bandgap layer 5 is in the reverse bias state, so for the entire secondary device, the current of the np-pn structure connected in series will depend on the reverse-biased structure, that is, the short-wave detection structure, working in the short-wave detection band, the photocurrent generated under short-wave light is the response of the device, but there is no response to long-wave light; on the contrary, when a negative bias is applied to the upper electrode, the photocurrent generated under long-wave light That is the response of the device, but there is no response to short-wave light. The bias voltage can be selected according to the following principles: the positive bias voltage only needs to be greater than the forward turn-on voltage of the long-wave pn junction with a certain margin, and the negative bias voltage only needs to be greater than the forward turn-on voltage of the short-wave pn junction with a certain margin. For convenience, the same positive and negative bias values can also be selected. The use of smaller positive and negative bias values is beneficial to reduce dark current and noise when the device is working. The situation is similar for the rear light input device, and it can be deduced by analogy that the direction of the bias voltage is opposite. Although this device has an npn structure, its p region is thick and is a highly doped wide bandgap material, so it will not produce triode or phototransistor effect under forward or direction bias, and it is still conventional for the two detection bands Photodiode.

Beneficial effects of the present invention

1. The PD or FPA of the present invention is a monolithic device made by an epitaxy method, and its vertical structure can be completed by one epitaxy, which is convenient to make;

2. The device of the present invention is a two-electrode device, only two contact electrodes are needed for a unit of PD or FPA, the structure is simple, and it is easy to connect with subsequent amplifiers or readout circuits;

3. The response band of the device of the present invention is conveniently controlled by the forward or reverse bias voltage applied to its two electrodes, and it is only necessary to properly arrange the subsequent amplification circuit or readout circuit, and the short-wave or long-wave signal can be According to specific application scenarios, select output or output in time sequence;

4. On the premise that InP is used as the substrate and the III-V lattice matching material system is used, the In _0.52 Al _0.48 As ternary system is a direct bandgap material with the widest forbidden band, and the In _0.53 Ga _0.47 As ternary system It is the narrowest direct bandgap material without antimony. Using In _0.52 Al _0.48 As as the short-wave absorbing layer can push the short-wave response wavelength of this dual-band detector to the shortest, and forming a pn junction in the wide-bandgap material can make the dark current of the short-wave device lower; using In _0.53 Ga _0.47 As is the long-wave absorbing layer, the long-wave response wavelength of the dual-band detector can be pushed to the longest; in this way, when In _0.52 Al _0.48 As is used as the short-wave absorbing layer and In _0.53 Ga _0.47 As is used as the long-wave absorbing layer, the short-wave response at room temperature The cut-off wavelength of the long-wave side is about 0.85 μm, covering the visible light band, and the cut-off wavelength of the long-wave side of the long-wave band is about 1.7 μm, covering an important range of the short-wave infrared band. Therefore, it is especially suitable for dual-band detection of visible light band and short-wave infrared band.

5. According to the aforementioned structure of the present invention, the upper and lower electrodes are all made on the n-type material in the process, so that compared with the conventional single-band devices that need to make electrodes and process separately on the p-type and n-type materials, it is more efficient at high There will be no difficulty in forming ohmic contacts on doped n-type materials, avoiding the difficulty of forming good ohmic contacts on p-type materials, and the upper and lower electrodes can be formed at the same time, which brings great convenience to the process and is conducive to obtaining better Device performance;

6. For FPAs with back light input, especially area array devices, the solution of this invention can still adopt the substrate removal method to further improve the short-wave response of the device without increasing the difficulty of the process;

7. In addition to the In _0.52 Al _0.48 As-In _0.53 Ga _0.47 As-InP material system with lattice matching, the present invention can also be realized on InAlGaAs-In _0.53 Ga _0.47 As-InP, InAlGaAs-InGaAsP-InP, InGaAsP -In _0.53 Ga _0.47 As-InP equivalent system materials, so that the cut-off wavelengths of short and long bands can be finely tailored and performance optimized, and can also be extended to InGaAs systems with extended wavelengths. The idea of the present invention can also be realized on other material systems.

Description of drawings

In order to further illustrate the concrete technical content of the present invention, accompanying drawing 2 pieces, specific description is as follows, wherein:

Figure 1. Spectral responses measured under forward and reverse bias voltages using Si and In _0.53 Ga _0.47 As PDs connected in series.

Fig. 2. Schematic diagram of the present invention, the left side is the front light input form, which is suitable for unit and line array devices; the right side is the back light input form, which is suitable for the area array devices where the readout circuits are directly interconnected. Specifically, it includes eight parts, namely: 1-semi-insulating InP substrate, 2-n-type highly doped InP lower contact layer, 3-lower contact electrode, 4-n-type low-doped In _0.53 Ga _0.47 As long-wave absorption layer, 5-p-type highly doped In _0.52 Al _0.48 As layer, 6-n-type low-doped In _0.52 Al _0.48 As short-wave absorption layer, 7-n-type highly doped In _0.53 Ga _0.47 As upper contact layer, 8- contact electrodes.

detailed description

To further illustrate the present invention, Fig. 1 shows the spectral responses measured under forward and reverse bias voltages after Si and In _0.53 Ga _0.47 As PDs are connected in series, both PDs are pn junction type The positive electrode of the device is connected, and the negative electrode of In _0.53 Ga _0.47 As-PD is used as the reference electrode (ground), and the negative electrode of Si-PD is used as the output electrode of the combined detector for outputting signals and applying bias voltage. It can be seen from Figure 1 that when a positive 1.5V bias is applied to this combination detector, since In _0.53 Ga _0.47 As–PD is in a forward bias, this combination detector exhibits a response spectrum of Si-PD, and In _0.53 Ga _0.47 As–PD The response of the combined detector is suppressed; when the negative 1.5V bias is applied to the combined detector, because the Si-PD is in the forward bias, the combined detector shows the response spectrum of In _0.53 Ga _0.47 As–PD, and the response of Si–PD is suppressed ; The bias value of 1.5 volts is much larger than the forward turn-on voltage of Si and In _0.53 Ga _0.47 As PD. This experiment has fully verified the reality and implementation points of the present invention.

Based on the above ideas, the present invention takes devices working in the two bands of visible light (including <0.85 μm near-infrared) and short-wave infrared (0.85 μm<wavelength<1.7 μm) as examples, and introduces them in III-V group In _0.52 Al _0.48 As - Two-electrode PD and FPA with dual-band bias control implemented on the In _0.53 Ga _0.47 As-InP material system to further illustrate the present invention. It should be understood that this embodiment is only used to illustrate a specific application example of the present invention, and is not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Fig. 2 shows a schematic diagram of the present invention, the left side of which adopts the front light input form, which is mainly suitable for unit and line array devices; the right side adopts the rear light input form, which is more suitable for area array devices directly interconnected with the readout circuit . Specifically, it includes eight parts, namely: semi-insulating InP substrate 1, n-type highly doped InP lower contact layer 2, lower contact electrode 3, n-type low-doped In _0.53 Ga _0.47 As long-wave absorption layer 4, p-type Highly doped In _0.52 Al _0.48 As layer 5 , n-type low-doped In _0.52 Al _0.48 As short-wave absorption layer 6 , n-type highly doped In _0.53 Ga _0.47 As upper contact layer 7 , and upper contact electrode 8 .

Example 1: front light input device

As shown on the left side of Fig. 2, for front light-emitting devices, firstly, molecular beam epitaxy (MBE) or metal-organic vapor deposition (MOCVD) is used to sequentially epitaxially grow n-type high-density crystals with matching lattices on semi-insulating InP substrates. Doped InP lower contact layer, n-type low-doped In _0.53 Ga _0.47 As long-wave absorbing layer, p-type highly doped In _0.52 Al _0.48 As layer, n-type low-doped In _0.52 Al _0.48 As short-wave absorbing layer and n-type high Doping the upper contact layer of In _0.53 Ga _0.47 As, and then using microelectronics technology to etch the mesa, after passivation, the lower contact layer of n-type highly doped InP and the upper contact layer of n-type highly doped In _0.53 Ga _0.47 As The lower contact electrode and the upper contact electrode are made on the top, and after the completion, the detector or focal plane chip is obtained by scribing, etc., and the subsequent processing and packaging are still carried out in the same way as the single-band device.

Example 2: back light input device

As shown on the right side of Fig. 2, for backside light-emitting devices, first, molecular beam epitaxy (MBE) or metal-organic vapor deposition (MOCVD) is used to sequentially epitaxially grow n-type high Doped InP lower contact layer, n-type low-doped In _0.52 Al _0.48 As short-wave absorbing layer, p-type highly doped In _0.52 Al _0.48 As layer, n-type low-doped In _0.53 Ga _0.47 As long-wave absorbing layer and n-type high Doping the upper contact layer of In _0.53 Ga _0.47 As, and then using microelectronics technology to etch the mesa, after passivation, the lower contact layer of n-type highly doped InP and the upper contact layer of n-type highly doped In _0.53 Ga _0.47 As The lower contact electrode and the upper contact electrode are made on the top, and after the completion, the focal plane chip is obtained by dicing, etc., and the In column is still made in the same way as the single-band device to interconnect with the readout circuit, and other processing and packaging are carried out.

Claims (4)

1. A dual-band InAlAs-InGaAs diode detector and focal plane array device with bias control, characterized in that the device is a stacked structure two-electrode photodetector or focal plane array device constructed by epitaxial methods on the same substrate The device is controlled by bias voltage to generate photoelectric response in two detection bands respectively. 2. A kind of bias-controlled dual-band InAlAs-InGaAs diode detector and focal plane array device according to claim 1, characterized in that a wide band gap matched with the InP substrate lattice is used in its laminated structure The ternary system In _0.52 Al _0.48 As and the narrow-bandgap ternary system In _0.53 Ga _0.47 As are used as short-wave and long-wave absorbing materials respectively, and the band gaps of the two materials correspond to the long-wave side cutoff wavelengths of the two bands of the device. 3. A kind of bias-controlled dual-band InAlAs-InGaAs diode detector and focal plane array device according to claim 1, characterized in that its short-wave response is produced by In _0.52 Al _0.48 As homogeneous pn junction, and its long-wave response is Produced by In _0.52 Al _0.48 As/In _0.53 Ga _0.47 As heterogeneous pn junction, all of them are photovoltaic devices working in photoconductive mode. 4. A kind of bias-controlled dual-band InAlAs-InGaAs diode detector and focal plane array device according to claim 1, characterized in that the monolithic two-electrode device adopts positive bias or negative bias That is to say, it can be controlled to generate corresponding photoelectric response of short-wavelength or long-wavelength and suppress the response of another waveband.