The effect of hydrogen plasma exposure on the deep level defects present in GaAs grown by molecular beam epitaxy (MBE) has been investigated by deep level transient spectroscopy and by photoluminescence. The three commonly observed defects in MBE grown layers, the M1, M2, and M4 levels, found to be present at a total concentration of 5×1013 cm−3, are completely passivated by exposure to the hydrogen plasma. At low carrier concentration, in samples where surface recombination is suppressed by a thin GaxAl1−xAs cap, passivation of these defects increases photoluminescence efficiency by factors of 30 and 100 at 298 and 77 K, respectively. Defect passivation occurs in addition to the previously reported donor neutralization, but, whereas the latter is removed by a 400 °C, 5 min anneal, the former remains fully effective. Only upon 600 °C, 5 min annealing does the defect level passivation begin to be lost. Thus there is a wide temperature window within which it is possible to regain the carrier concentration without loss of passivation of the deep level defects.

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The problem of hydrogenation ofInP without surface degradation has been surmounted by exposure of the InP surface to a hydrogen plasma through a thin SiN); (H) cap layer. This layer is H permeable at the hydrogenation temperature of 250 °e, but P or PH J impermeable thus minimizing PH 3 10ss and the attendant In droplet formation. In contrast to our results for this type of plasma exposure of GaAs, we find that shallow acceptors in InP are heavily passivated, whereas shallow donors are only very weakly affected. For exampie,p r--InP(Zn) of 3 X 10 18 cm-3 has its residual hole concentration reduced to <;3 X 10 14 cm-3 over a depth of 1.3 pm by a 250 ·C, 0.5 h deuteration. The presence of acceptors impedes H (or D) indiffusion, as indicated by D diffusion under the same conditions occurring to depths of 18 and 35 pm inp-InP (Zn, 2x 10 16 cm--3 ) and n-InP (5 or Sn), respectively. Annealing for 1 min at 350°C causes the acceptor passivation to be lost and the hole concentration to be returned to its prehydrogenation level, indicating that the passivation has similar thermal stability to that of acceptors in GaAs, but lower than that of donors.

We report detailed studies of the low-temperature photoluminescence of Cd-related centers in InP. The samples consisted of Cd-diffused InP substrates as well as Cd-doped InP epitaxial layers grown by metalorganic chemical vapor deposition. Besides the previously identified 1.365-eV band, a new Cd-related band at a lower photon energy is reported. At 5.5 K, depending upon the excitation intensity, the peak position of this new band lies in the energy range 1.20–1.33 and 1.33–1.34 eV, respectively, in the substrates and in the epitaxial layers and it is broader compared to the 1.365-eV band. The peak position of the bands shifts to higher energy with increasing excitation intensity but the change in the peak energy per decade change in excitation intensity is much larger (50 meV) for the lower-energy band compared to the 1–2 meV shift for the 1.365-eV band. While the excitation dependence of the bands suggests a donor-to-acceptor pair recombination for their origin, we present arguments to show that the larger shift of the peak energy of the lower-energy band with excitation intensity is perhaps a consequence of the involvement of a deep donor in its origin as opposed to a shallow donor in the 1.365-eV band. In the case of InP:Cd substrates both the 1.365-eV band and the 1.20–1.33-eV band exhibit thermal quenching of luminescence above 100 K with an activation energy of 54±4 meV which is comparable to the ionization energy of 56 meV for the substitutional Cd acceptor, CdIn . From this we infer that both bands involve the CdIn acceptor in the recombination process. The identity of the deep donor in the 1.20–1.33-eV band and that of the recombination centers giving rise to the 1.33–1.34-eV band in the InP:Cd epitaxial layers are not known. In a preliminary comparison study on InP:Zn, similar, high- and low-energy Zn-related bands are observed. It is suggested that the deep donor is related to the group II impurity.

Stress-strain curves are presented for Si-doped GaAs single crystals deformed in compression parallel to and <111> at temperatures ranging from 250" t0550"C. In both orientations, slip occurs only on { 111) <110>. Repeatedyielding experiments on GaAs crystals, both undoped and doped with Si, Cr, or Zn, indicate that Si-doped crystals (ntype) have a greater yield stress than undoped crystals, that undoped crystals have a greater yield stress than Zn-doped crystals @-type), and that Cr doping does not significantly affect the yield stress. Extensive crack formation resulting from deformation was not observed. Compression specimens normally failed by breaking into several columnar fragments with their long dimension parallel to the stress axis.