Bertram Schwartz

Germanium‐Doped Gallium Arsenide

Germanium‐doped GaAs crystals were grown on GaAs seeds from Ga solution. The properties of the Ge‐doped GaAs layers were examined by Hall effect measurements from 20° to 400°K and by photoluminescence measurements between 12° and 300°K. It was found that Ge‐doped GaAs is always p‐type when grown at 900°–875°C from Ga solution containing 56 at.% or less Ge. The temperature dependence of the Hall coefficient and the photoluminescence experiment indicated an acceptor energy level of 0.035 and 0.038 eV respectively. It was also found that at least 85% of the Ge was present as an acceptor in the GaAs crystals when the growth solution contained two atom percent or less Ge.

Optical properties of anodically grown native oxides on some Ga‐V compounds from 1.5 to 6.0 eV

Complex refractive‐index and dielectric function data are given for anodically grown native oxides on GaP, GaAs, and GaSb from 1.5 to 6.0 eV. The absorption thresholds for the oxides on GaAs and GaSb occur at 5.0 and 4.2 eV, respectively, with weak tails extending 0.5 eV to lower energy. The absorption threshold in GaP is not seen but is estimated to be near 7 eV. A comparison of these data with each other and with those for SiO2 and GeO2 suggests a more complex bonding behavior than a simple amorphous phase.

Raman scattering from anodic oxide‐GaAs interfaces

The nature of the interface between anodically grown oxide films and gallium arsenide substrates was studied using Raman backscattering. Room‐temperature spectra of GaAs covered with as‐grown anodic films as well as anodized samples dried under nitrogen at 250°C showed only the first‐order longitudinal (LO) and transverse (TO) optical modes and the less‐intense two‐phonon features of the GaAs substrate. Heating the films at 450°C and above results in the appearance of intense LO (257 cm−1) and TO (198 cm−1) bands due to crystalline arsenic and the structureless Raman scattering near 200–250 cm−1 due to amorphous arsenic. Polarized Raman spectra indicate that elemental arsenic is not an intrinsic oxidation product of the room‐temperature anodization. We suggest that the thermally induced solid‐state interfacial reaction, As2O3+2GaAs→Ga2O3+4As, is responsible for the presence of arsenic at the oxide‐semiconductor interface following annealing.

The combined use of He back-scattering and He-induced X-rays in the study of anodically grown oxide films on GaAs☆

Abstract Anodic oxide films on GaAs have been studied by the combined use of He back-scattering and He-induced X-rays. Back-scattering is hampered by the lack of mass resolution between Ga and As. X-ray analysis has excellent mass resolution but poor depth resolution. This poor depth resolution is overcome by increasing the effective thickness of the films by entering at grazing angles and making use of the property that the He-induced X-ray cross sections fall steeply with decreasing energy. This technique and the methods of data analysis are discussed in detail. The anodic oxide films are found to be deficient in As within 200 A of the surface and to have a Ga:As ratio of approximately 1:1 for the rest of the oxide. On heating to 650°C most of the As diffuses out of the films.

High resistivity in InP by helium bombardment

Helium implants over a fluence range from 1011 to 1016 ions/cm2, reproducibly form high resistivity regions in both p‐ and n‐type InP. Average resistivities of greater than 109 Ω cm for p‐type InP and of 103 Ω cm for n‐type InP are reported. Results are presented of a Monte Carlo simulation of helium bombardment into the compound target InP that yields the mean projected range and the range straggling.

Rapid thermal annealing of dopants implanted into preamorphized silicon

The rapid thermal annealing behavior of BF+2 and As+ +BF+2 implanted into crystalline and preamorphized silicon is studied. After solid phase epitaxy nearly complete electrical activity is obtained without channeling tails (for the preamorphized silicon) or significant thermal diffusion. Dislocation loops always appear near the amorphous‐crystalline (α/c) interface of the preamorphized layer after solid phase epitaxy annealing (called ‘‘deep disorder’’). For preamorphization using Si+ damage into room‐temperature silicon targets, dislocations also span between the deep disorder and the surface, called ‘‘spanning dislocations.’’ The spanning dislocations are eliminated by preamorphization using Ge+ implanted into room‐temperature silicon targets. Transmission electron microscopy studies show the spanning dislocations move to the surface under thermal treatment, while the deep disorder remains to act as a getter region. The deep disorder is shown to getter F, or Au when Au is intentionally diffused from the...

Annealing behavior of ion‐implanted Fe in InP

The annealing behavior of implanted Fe+ in InP is studied using secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). Dual implants (275 keV, 1.25×1014 cm−2 and 400 keV, 1.25×1014 cm2) were performed at room temperature (RT) and at 200 °C and then annealed at 725 °C for one hour. TEM reveals a 3100‐A amorphous region in the unannealed RT implant. Significant defect production is observed in this sample at the amorphous‐crystalline interface following the anneal. SIMS reveals an Fe pileup at this interface. No such pileup is observed in the samples implanted at 200 °C. The data also suggest an Fe diffusion constant which is lower than typically reported in the literature. The results are contrasted with the SIMS study by M. Gauneau, H. L’Haridon, A. Rupert, and M. Salvi [J. Appl. Phys. 53, 6823 (1982)].

Channeled substrate buried heterostructure InGaAsP/InP laser employing a buried Fe ion implant for current confinement

A channeled substrate buried heterostructure InGaAsP/InP laser is demonstrated using a hybrid technique of Fe ion implantation followed by liquid phase epitaxy. A high resistivity region is formed by the implantation and subsequent anneal of Fe into an n‐type InP substrate, and this is used to provide a self‐aligned current confinement barrier layer. The use of an in situ anneal prior to liquid phase epitaxy minimizes the number of processing steps. Pulsed threshold currents as low as 22 mA have been achieved on devices utilizing broad area metal contacts.

Picosecond photoresponse in 3He+ bombarded InP photoconductors

3He+ bombardment is shown to be an effective means of achieving free‐carrier lifetimes as short as 1 ps in Fe‐doped InP without compromising the dark resistance of the photoconductor. Autocorrelation measurements demonstrate that these bombarded photoconductors operate as sampling gates with 2‐ps sampling apertures and millivolt sensitivity. They exhibit a 10–90% decay time of 30 ps when used as pulse generators; we attribute this behavior to imperfect contacts.

Integrated multijunction GaAs photodetector with high output voltage

Integrated structures consisting of two P‐I‐N double heterostructure GaAs photodetectors, series connected by means of a tunnel junction, have been fabricated by molecular beam epitaxy. Open‐circuit output voltages, external power efficiencies, and fill factors were 1.777 V, 33.4%, and 0.83, respectively, for antireflection‐coated cells excited by ∼5 mW optical power from a focused DH AlGaAs laser emitting at λ=0.815 μm.