RU1787297C - Optoelectronic device - Google Patents

Abstract

Usage: in semiconductor quantum electronics. SUMMARY OF THE INVENTION: An optical integrated circuit contains a laser and pnp bipolar phototransistor elements separated by an optically transparent layer. The restriction on the location of the optically transparent layer and the concentration of the main charge carriers in this layer, as well as the restriction on the concentration of the main charge carriers of the layers forming the collector junction of the bipolar phototransistor, provide the necessary and sufficient level of internal electric and optical coupling for effective modulation gain in the active region of the laser element. 2 ill.

Description

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The invention relates to quantum electronics and can be used in semiconductor optoelectronics.

Devices are known in which optical and electronic modulating elements are integrated into a hybrid circuit. The mode of deep high-frequency relaxation pulsation in them is realized by generating picosecond electric pulses generated by diodes with accumulation of charge or by avalanche transistors. However, due to the presence of spurious reactances in hybrid optoelectronic devices, the ability to control the amplitude and shape of the modulating signal is noticeably limited, and, as a result, the pulse power does not exceed 200 mV when modulating optical pulses of 50 ps duration.

1 The closest technical solution, selected as a prototype, is an optoelectronic device containing a bipolar phototransistor and a laser element, made in the form of a multilayer structure based on A3B semiconductors, including the l + substrate: k and arranged in series p, p, p-, p-, p + layers, where the p + - pn layers form the phototransistor, and the p-pr + laser elements, and three electrodes, two of which form contact with the substrate and the p + layer.

The vertical arrangement of the laser and bipolar phototransistor elements reduces spurious reactivity, and the presence of positive electrical and optical feedback expands the functionality of optoelectronic XI 00

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device. Meanwhile, the optical and electronic elements forming the optoelectronic device do not provide high-frequency relaxation pulsation, since the amplitude of the electric signal is limited to several hundred milliamps, and the current rise time lies in the nanosecond duration range. In this case, the combination of large amplitudes and small durations of current rise is fundamentally excluded. The fundamental limitation is associated with the well-known Kirk effects, the displacement of the current to the edge of the emitter transition, etc. As a result, the power of optical pulses in the optoelectronic device is limited and does not exceed 100 mW.

An object of the invention is to increase the power of ultrashort pulses. The physical nature of the proposed solution is based on the use of an avalanche breakdown of a phototransistor initiated by a light flux from a laser element.

Figure 1 shows the design of an optoelectronic device; Fig. 2 is an electrical wiring diagram.

The optoelectronic device contains an electrode 1 to the substrate 2, as well as the base and collector layers 3 and 4, which form the collector junction of the p + -pn bipolar phototransistor. The emitter 5 of the laser element also contains an active region 6 directly adjacent to the collector layer 4 of the phototransistor bounded by layers 5 and 7. An electrode 9 is made to the emitter 5 of the laser element, and an electrode 9 is made to the layer 7.

The switching circuit shown in FIG. 2 contains a voltage source 10, limiting the resistance of the charging line Ry 500 kOhm 11, a segment of coaxial cable 12, the length of which sets the duration of the laser pump pulse, limiting the resistance of the control circuit RH 500 Ohm 13, generator 14 pulses, Optoelectronic device 15, load resistance RH 50 Ohm 16.

When a control pulse is supplied through an electrode 8 made to the emitter 5 of the laser laser + structure, minority charge carriers are injected into the active region b of the laser element of their recombination with the emission of light quanta. At this stage, the laser element is in a subthreshold generation mode. The design of the optoelectronic device is such that most of the photon flux enters the collector 4 and is absorbed in the region of the bulk charge of the collector pn junction of the phototransistor. In order to localize most of the voltage drop in the optical absorption region (the characteristic size of the self-absorption region is 10 μm), the collector

The pn junction of the phototransistor is formed on the basis of layers with a concentration of dopant N 1015. In this case, the lower limit of concentration values is determined only by the capabilities of technological

modes of formation of the p - pn structure of the phototraistor and is currently N 10. .

Injected carriers during the passage of the spatial charge region

the collector pn junction reaches the threshold ionization energy EI and impact ionization becomes possible if the voltage at the pn junction is greater than the avalanche breakdown voltage UB and the width

the spatial charge region corresponds to the maximum field strength during breakdown. Based on the experimental dependences of the avalanche breakdown voltage and the maximum field Em on the dopant concentration for pn junctions based on gallium arsenide, the minimum voltage value UB 25QB is established, starting from which shock mechanism

ionization in n + -p-n-structures of the phototransistor element with a concentration of dopant,

The minimum voltage value UB 250 V determines the lower limit.

layer thickness sufficient to accommodate the spatial charge region. collector pn junction - W:

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The positive electrical and optical coupling of the constituent elements of the elements is such that not only laser photo-reception is achieved by the bipolar phototransistor, but also the amplification of the received signal. The latter means that the thickness of the layers forming the collector pn junction of the phototransistor is such that at least it satisfies the inequality

o- 1 - W2 / 2L2 0.5 or,

where L is the diffusion length of the nonequilibrium charge carriers in the base of the phototransistor. The diffusion lengths for gallium arsenide with a dopant concentration of N 1015 cm 3 are in the range of 15100 microns. Assessment of the thickness of the layers forming the collector p-n junction is performed in accordance with the distinctive part of form 11/2

mules of the invention Irr r - Tu l. SW L,

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indicates compliance of the obtained values with the specified range. In other words, the limitation of the total thickness W of the layers given in the characterizing part of the claims is a necessary and sufficient condition for the operability of the proposed optoelectronic device.

Example. The structure was fabricated by liquid epitaxy. On n + - GaAs substrates, a high voltage collector pn junction of a bipolar phototransistor based on weakly doped gallium arsenide with a carrier concentration of N (10 ™ - 5–1014) was first grown. The total layer thickness did not exceed 50–55 μm, which ensured the avalanche voltage a sample of UB 250 V. Then, a heterostructure of a laser element containing a wide-band-gap emitter layer, two undoped waveguide layers surrounding a quantum-well active region, and a second w were grown by low-temperature liquid-phase epitaxy. rokozonny layer p + -AlxGai-xAs. The optically transparent broad-gap n-layer of the emitter of the laser element doped with Te to a level of 51 10 cm limited, on the one hand, the active region of the laser element and, on the other, the spatial charge region of the high-voltage bipolar phototransistor. In the manufacture of laser resonators with mirror faces, etching or cleaving in the cleavage plane were used.

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The avalanche mode of the optoelectronic device according to the circuit shown in Fig. 2 provided a modulating electric pulse with an amplitude of 5-10 A for less than 200 ps. The optical pulse power was 3 W for a duration of less than 20 ps. Estimates show that the proposed structure at a pump level of 3-5 KA / ms2 is capable of generating optical pulses with a power of more than 20 W from one face of a laser element with a pulse duration of 10 ps.

Claims (1)

The claims .Optoelectronic device containing a bipolar phototransistor and a laser element, made in the form of a multilayer structure Based on semiconductors AB, including an n + substrate and arranged in series p, n, n, p, p + layers, and the substrate and pn layers form a phototransistor and pnp laser elements, and 3 electrodes, two of which form contact with a substrate and a p + layer, characterized in that, in order to increase the power of ultrashort pulses, n - and p-layers forming the collector junction of the phototransistor are made at the end Nation selected in  13 ° hp ° the interval 10 ° N 1015, and the total thickness W of both layers 25011/2  where L is diffusion the length of nonequilibrium charge carriers in the base of the phototransistor, q is the charge of the electron, Ј is the dielectric constant, and the third electrode is made to the n-layer, which is the emitter of the laser p-p-p-structure. 12 fifteen