A planar InP/InGaAsP heterostructure avalanche photodiode

A new guard-ring structure for InP/InGaAsP heterostructure avalanche photodiodes (APD's) is presented. The guard ring consists of a linearly graded junction formed by beryllium ion implantation and two-step InP layers having different carrier concentrations (n-and n-layers grown on an InGaAsP layer). A planar InP/InGaAsP avalanche photodiode having this guard ring has a maximum avalanche gain of 110 at an initial photocurrent of 0.35 µA. The effectiveness of the guard ring is clearly discernible from the spot-scanned photoresponse of the diode.     

Planar InP avalanche photodiode with Zn-diffused guard ring

A guard ring structure with a p+-n?-n junction formed by Zn diffusion at 450°C gave a high gain planar InP avalanche photodiode. A maximum multiplication factor of more than 50 was obtained uniformly within the photosensitive area without edge breakdown.     

Diffusion of Cd And Zn In InP between 550 and 650°C

A large number of diffusions have been carried out in sealed quartz ampoules in the temperature range 550–650°C using Zn and Cd in InP. Three-fronted profiles were observed at 650°C for both Cd and Zn and the diffused samples were extensively analysed using Hall measurements, electron beam induced current, electrochemical carrier concentration profiling and thermal probing. These electrical measurements identified the p/n junction unambiguously and indicated a region of high compensation between the p/n junction and the third line. The weight of P added to the ampoule had little effect up to 0.4mg in 0.75cm³ volume at which point a dramatic reduction in diffusion depth for all fronts occurred for increasing P. Diffusion coefficients for Cd and Zn were estimated and plotted as a function of temperature.     

Bias-temperature life tests for planar-type VPE-grown InGaAs/InP heterostructure APD's

The fabrication processings and the preliminary bias-temperature life tests for planar-type InGaAs/InP heterostructure avalanche photodiodes (HAPD's) made from VPE-grown wafers are presented. The plasma deposited SiNxpassivation film showed a surface state density Nssof less than 10¹²cm^-2. eV^-1. An anomalous behavior of Cd diffusion velocity was observed in the process of the guard-ring formation. A Cr/Au p-side electrode made it possible to reduce the contact failure compared to an Au/Zn contact. Bias-temperature life tests were carried out at three temperature levels: 80, 120, and 180°C. Low-bias life tests (V_{R} = 10V) were tried at first for the diodes without a guard-ring structure for times exceeding 10 000 h. The HAPD's with the guard-ring have been tested under the condition of high electric field (>4 times 10^{5}V/cm). The stable devices have been operating up to 6000 h under the high field condition even at 180°C. The HAPD's are still at the prototype stage. Thus, the test results are considered to be encouraging as to achieving highly reliable photodiodes.     

Planar Zn diffusion in InP

A procedure for achieving well-behaved planar Zn diffusion to a controllable depth in n-type InP is described. The dilute-Zn diffusion, which utilizes a Zn+Ga+P source (in an evacuated ampoule), is performed in the temperature range 650–700°C. The low diffusion temperatures employed assure that any previous junctions that might be prepared, such as LPE heterojunctions, are not affected by the diffusion process. The masking afforded by Si₃N₄ and partial “masking,” or attenuation, afforded by SiO₂ on InP are demonstrated. The results obtained suggest that dilute-Zn diffusion in InP, with a significant P over-pressure, favors a substitutional diffusion mechanism that probably follows a complementary error function distribution.     

InGaAs/InP separated absorption and multiplication regions avalanche photodiode using liquid- and vapor-phase epitaxies

Heterostructure planar InGaAs/InP avalanche photodiodes, which consist of a vapor-phase epitaxial InP avalanche multiplying layer and a liquid-phase epitaxial In0.53Ga0.47As optical absorption layer, were fabricated. Dark current, multiplication, spectral response, and pulse response characteristics are reported. Diodes were prepared by InGaAs liquid-phase epitaxy on an InP substrate, followed by InP vapor-phase epitaxy. The vapor-phase epitaxy was adopted in the InP growth to avoid ternary layer melting encountered in the liquid-phase process. Cd diffusion was carried out in the InP layer to form a p-n junction. A uniform multiplication factor of 5.5 was observed without a guard ring. The quantum efficiency was 70 percent in the1-1.6 mum wavelength region without antireflection coating. Dark current density was as low as1.5 times 10^{-4}A/cm²at 90 percent of breakdown voltage. A fast rise time of 100 ps was observed.     

Anomalous Lateral Zn Surface Diffusion in InP Caused by Zn-Contained Metallization

We report an anomalous Zn surface diffusion in InP during annealing of ohmic contact structures containing Zn. A Pd/Zn/Pd contact was used to demonstrate this phenomenon. Electrical properties of the contact were monitored to corroborate this anomalous surface diffusion. Cross-sectional scanning electron microscopy was also used to delineate the Zn diffusion front lines. It was found that the Zn surface lateral diffusion can extend ≥50 μm for samples annealed at 500°C or higher temperatures. Close attention should be paid to this anomalous lateral surface diffusion during fabrication of devices using Zn-contained ohmic contacts.     

Oxide defined TJS lasers in InGaAsP/InP DH structures

Transverse junction stripe lasers in the InGaAsP-InP systems have been fabricated by Zn diffusion through oxide windows into DH structures of InGaAsP/InP with all epitaxial layers n-type. The quaternary layer composition is such that room temperature laser emission is at 1.18 μm. TJS laser mode behavior with accompanying single longitudinal mode operation and kink-free light-output characteristics are seen at 77 K. As the temperature is increased, this behavior persists up to about 130 K, when parallel electron injection through the p-n junction in the InP layers becomes so large that, in parallel with the TJS laser filament, a normally operating DH laser filament starts operating. At higher temperatures only the latter is seen to operate.     

Planar InP/InGaAs avalanche photodiodes with preferential lateral extended guard ring

High-speed and high-sensitivity planar InP/InGaAs avalanche photodiodes (APD's) have been fabricated with a newly developed preferential lateral extended guard ring (PLEG). By employing the configuration, avalanche photodiode yield was markedly improved without edge breakdown. Received powers required to give 10^-9bit-error rate (BER) at 1.55-1.57-µm wavelength were -44.5 and -37.4 dBm for 450 Mbit/s and 2 Gbit/s, respectively.     

Reliability of InGaAs/InP long-wavelength p-i-n photodiodes passivated with polyimide thin film

The long-term reliability of InGaAs/InP p-i-n photodiodes passivated with polyimide thin film was studied through a room temperature life test and through thermally accelerated life tests. No degradation in dark current was observed in a room temperature life test at a reverse bias of -15 V after aging for 7000 h. However, the dark current increased gradually in the accelerated life tests at 110°C, 130°C, and 150°C. It was confirmed that the activation energy of degradation in dark current was 0.85 eV and the average lifetime was estimated to be 10⁷h at room temperature. The dark current recovered in high temperature storage tests. The phenomenon of degradation and recovery was qualitatively explained by a model of accumulation and diffusion of mobile ions at a junction perimeter.     

InGaAsP InP current confinement mesa substrate buried heterostructure laser diode fabricated by one-step liquid-phase epitaxy

New InGaAsP/InP buried heterostructure laser diodes fabricated by one-step liquid-phase epitaxy are described, in which the InGaAsP active region completely embedded in InP is grown on the top of the mesa stripe formed on the InP substrate while, simultaneously, current confinement structure is automatically formed on both sides of the mesa stripe. These current confinement mesa substrate buried heterostructure laser diodes (CCM-LD's) have current confinement structure which very effectively blocks unwanted leakage current bypassing the light emitting region which has enabled laser operation with a threshold current as low as 20 mA, 70-mW maximum CW output at room temperature, and 125°C maximum CW operation temperature. Life tests over 6000-h CW operation at 70°C and 5 mW/facet have confirmed good reliability of these devices.     

闭管扩散Zn对InP表面性质的影响

利用闭管扩散方法以Zn3P2为扩散源，在不同扩散温度和扩散时间下对非故意掺杂InP (100）晶片进行扩散. 用电化学C-V法（ECV）和二次离子质谱法(SIMS)分别测出了空穴浓度和Zn的浓度随深度的分布曲线. 结果表明扩散后InP表面空穴和Zn的浓度在扩散结附近突然下降，InP表面空穴浓度主要取决于扩散温度，扩散深度随着扩散时间的增长而变大，InP表面Zn浓度一般比空穴浓度高一个数量级. 另外对扩散后的样品进行光致发光（PL) 测试，表明在保证表面载流子浓度的同时，适当降低扩散温度和增加扩散时间能减小对InP表面性质的影响.     

Low dark-current, high-efficiency planar In0.53Ga0.47As/InP P-I-N photodiodes

We have fabricated high quantum efficiency, high speed, low dark-current In0.53Ga0.47As/InP p-i-n planar photodiodes Which meet the performance requirements of long-wavelength optical communications systems. The diodes employ plasma deposited SiNxas a mask to Zn diffusion. The dark-current density at 10 V is J = 5 × 10^-5A/cm²with a corresponding capacitance of C = 5 × 10^-9F/cm².     

Zn在InP中低温扩散的研究

本文用Zn3P2源在闭管条件下研究了Zn在InP中的低温(520700℃)扩散。比较了用等温扩散和双温区扩散技术扩散后,样品的电学参数。结果表明:双温区扩散法可得到表面光亮,无损伤的高浓度表面层。该法已用于InGaAsP/InP双异质结发光管的制备工艺中,并制得了光功率1mW,串联电阻23的发光管。还讨论了Zn在InP中扩散时的行为,解释了低温(550℃)扩散过程中,等温扩散时出现的异常现象。     

A groove GaInAsP laser on semi-insulating InP using a laterally diffused junction

Low threshold current GaInAsP/InP groove lasers have been fabricated on semi-insulating InP substrates. Three n-type layers are grown with a single liquid phase epitaxial (LPE) growth process, and the p-n junction is formed by a lateral Zn diffusion. The active layer inside the groove provides a real index waveguide. Threshold currents as low as 14 mA with 300 μm cavity length are obtained. A single longitudinal mode at 1.3 μm up to1.4 I_{TH}is observed. The lasers operate with a single lateral mode when the active region width is less than 2.5 μm. This laser is suitable for monolithic integration with other optoelectronic devices.     

A planar InP/InGaAs avalanche photodiode with floating guard ringand double diffused junction

The authors discuss the fabrication, performance, and design of a novel, planar In_0.53Ga_0.47 As/InP separate absorption and multiplication region avalanche photodiode (SAM-APD) with floating guard rings and a double Zn diffused junction. The APD, grown by both vapor phase epitaxy and metalorganic vapor phase epitaxy, is observed to have a uniform gain of 85, a minimum primary dark current density of 5×10^-6 A/cm² at 90% of breakdown, and a capacitance of 0.4 pF for a front-side illuminated device. Both experimental and analytical results show that the double-diffused floating guard ring structure prevents edge breakdown, and also greatly reduces the electric field along the semiconductor/insulator surface. The operation mechanisms and the optimum design of the planar APD based on a two-dimensional device model are discussed     

A study of Zn diffusion in InP at low temperature

The diffusion of Zn in InP at low temperature is investigated. The experiment is accomplished in an evacuated and sealed quartz ampoule using Zn_eP₂ as the source of Zn. The electrical characteristics of the diffusion samples obtained by the isotemperature process and the two-temperature process have been compared. It is found that with the two-temperature process one can obtain a smooth, damageless and high-concentration surface layer. This process has been applied to fabricate InGaAsP/InP light emitting diodes, and the diodes obtained have an output power of ≥1mW with a series resistance of 2–5Ω. The behaviors of Zn diffusion in InP are discussed.     

Cd和Zn在InP中扩散的研究

本文介绍了在450700℃的广阔温度范围内研究Cd和Zn向InP扩散的结果,并对结果作了比较。详细研究了Cd,Zn及其化合物等不同杂质源对扩散的影响。我们用结深(xj)的平方和时间(t)的比值(xj2/t)作为扩散速度的度量,并画出了xj2/t-1/T(温度)曲线。发现Cd源,特别是CdP2源的扩散速度较慢,容易控制它扩散的结深和浓度,昕以它是比较理想的扩散杂质源。利用Tien的中性复合体理论,解释了Cd和Zn在InP中扩散的复杂现象。     

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace.The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements.The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission,which indicates that Zn was commendably diffused into InP layer as the acceptor.High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 ℃ for 10 min.Furthermore,more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process.Based on the above Zn-diffusion technique,a 50μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of-5 V and a high breakdown voltage of larger than 41 V (I ＜ 10 μA).In addition,a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.     

Reactions between Pd thin films and InP

The reactions between Pd thin films and (001) oriented InP have been studied in detail. Palladium was deposited on InP by electron beam evaporation to a thickness of 60 nm. Specimens were then annealed in vacuum at temperatures up to 500° C for as long as several days. An amorphous ternary phase (Pd≈₃InP) formed during deposition. During annealing, several crystalline ternary phases were detected. Pd₂InP and Pd₅InP were detected at lower annealing temperatures,i.e. from 225–275° C. Pd₂InP grew first, exhibiting an epitaxial relationship with InP, followed by preferred growth of Pd₅InP within the Pd₂InP layer. Both phases later decomposed (≈400° C) producing Pd₂InP(II), which also grew epitaxially on InP. At temperatures greater than 400° C, Pd₂InP(II) decomposed to Pdln and PdP₂, which were thermodynamically stable in contact with InP.