F. R. Shepherd

Metalorganic chemical vapor deposition InGaAs p‐i‐n photodiodes with extremely low dark current

Planar, Zn‐diffused InP/InGaAs p‐i‐n photodiodes, which have been fabricated from material grown by metalorganic chemical vapor deposition, have been shown to exhibit extremely low dark current. The typical dark current measured for 100‐μm‐diam devices was 10 pA at −10 V bias, with some devices having values as low as 3 pA (3.8×10−8 A/cm2). Excellent uniformity of the dark current was found. A low capacitance of 0.45 pF, a responsivity at 1.3 μm of 0.90 A/W, and rise/fall times of less than 150 ps were measured at −5 V bias.

Zinc‐enhanced beryllium redistribution in GaAs/GaAlAs grown by molecular beam epitaxy

A study of the effect of zinc diffusion into beryllium‐ and silicon‐doped GaAs/Ga0.7Al0.3As structures has been carried out. The beryllium dopant was found to diffuse very rapidly as a result of the presence of diffusing zinc, while the silicon remained unaffected. A mechanism is proposed whereby competition for the gallium sites causes the beryllium to move interstitially wherever zinc is present.

Ion implantation damage of InP and InGaAs

Abstract The damage accumulation and annealing processes in ion bombarded InP and InGaAs have been studied. Epitaxial InGaAs layers on (100) oriented InP and InP crystals were implanted with 16 O ions to produce a R p of 0.5 μm in each material for ion doses from 10 13 to 2 × 10 16 cm −2 , implant temperature from 80 to 373 K, and beam flux from 0.01 to 1.8 μA cm −2 . The retained damage following implantation was analyzed by the Rutherford backscattering/channeling technique. The results show that the response of each material to O ion bombardment is widely different for all implantation temperatures. Within the flux range studied, amorphous layers can be formed in InP at all temperatures up to 373 K for 16 O fluences ≥ 5 × 10 14 cm −2 . Strong dynamic defect annealing precludes amorphization of InGaAs at 290 K for O doses up to 5 × 10 15 cm −2 and beam flux up to 1.8 μA cm −2 .

Room‐temperature annealing of Si implantation damage in InP

Spontaneous recovery at 295 K of Si implant damage in InP is reported. InP(Zn) and InP(S) wafers of (100) orientation have been implanted at room temperature with 600 keV Si+ ions to doses ranging from 3.6×1011 to 2×1014 cm−2. Room‐temperature annealing of the resultant damage has been monitored by the Rutherford backscattering/channeling technique. For Si doses ≤4×1013 cm−2, up to 70% of the initial damage (displaced atoms) annealed out over a period of ≊85 days. The degree of recovery was found to depend on the initial level of damage. Recovery is characterized by at least two time constants t1<5 days and a longer t2≊100 days. Anneal rates observed between 295 and 375 K are consistent with an activation energy of 1.2 eV, suggesting that the migration of implant‐induced vacancies is associated with the reordering of the InP lattice.

Influence of dose rate and temperature on the accumulation of Si-implantation damage in indium phosphide

The influence of dose rate and temperature on the implantation damage accumulation in InP has been investigated. InP crystals were implanted at 80–323 K with 600 keV Si+ ions at a beam flux of 0.005–1.0 μA cm−2, and to total fluences of between 5×1012 and 2×1014 Si cm−2. The residual damage following implantation was analysed by the Rutherford backscattering/channeling technique. The results show that at 80 K, the influence of the beam flux on the accumulated displacement damage is small. However, at T≥295 K the displaced atom density, Nd, exhibits a power law dependence on J:Nd=αJn, with the value of n dependent on both the total ion dose and implant temperature. At 295 K and Si doses of 1–4×1013 cm−2, the value of n varies from 0.23 to 0.15.

Wafer scale processing of InGaAsP/InP lasers

Chemically assisted ion beam etching (CAIBE) and electron cyclotron resonance (ECR) plasma deposition have been used to etch and coat 1.3 μm InGaAsP/InP heterostructure lasers in full wafer form. Ar/Cl2 CAIBE, using an ECR dual grid ion source, was used to etch 4 μm deep vertical (90°±0.5°), smooth facets at rates up to 1.3 μm/min. An integrated back facet monitor was simultaneously fabricated in the same heterostructure. High‐reflectivity Si/SiO2 optical coatings were deposited on the etched facets by low‐temperature (<120 °C) ECR plasma deposition and selectively patterned by liftoff. Full wafer testing of the processed devices showed good uniformity (±3%) with laser threshold currents of 25 mA and a slope efficiency of 0.23 W/A at 25 °C and 0.11 W/A at 85 °C. Back facet monitor efficiency was 0.4 A/W over the whole temperature range.

Analysis of Zn redistribution in MOCVD InP layers

Although Zn is the source of p‐type doping mostly used during MOCVD of InP, it is also known that Zn diffuses rapidly in InP at temperatures typically used for the MOCVD growth (∼900K). In this paper we investigate outdiffusion of Zn from InP MOCVD layers into adjacent n‐type InP spacer layers. Alternating p‐type layers (1/2μm, undoped or Si‐doped with 1015<CSi<1×1019 cm−3) were grown by low pressure MOCVD. The distribution of Si and Zn was determined by SIMS, using implanted standards to calibrate the data. For undoped InP spacer layers, the Zn completely diffused across the spacer layers during growth (1–2 hours). When the Si concentration in the spacer layers was increased, the extent of Zn out diffusion during growth was dramatically reduced. For CSi<CZnZn outdiffused into the spacer layer until CZn∼CSi, at which point the Zn concentration fell steeply. Conversely for CSi≫CZn, no outdiffusion of Zn during continued growth of overlayers was detected. This behavior is similar to that found for Zn diffus...