Byung Doo Choe

Correlation of electrical carrier and atomic profiles of Mg implants in GaAs

A comparative study of secondary ion mass spectrometry (SIMS) atomic profiles and electrical profiles for S‐implanted GaAs has been made. For all doses, the electrical profiles are in good agreement with the SIMS profiles in the deep side of the samples, where there is no significant implantation damage. For low dose, the implanted S undergoes substantial redistribution during thermal annealing throughout the entire implanted region while for high dose, S redistributes to a much lesser extent in the implanted peak region. It is suggested that unannealed implantation damage and S precipitation are responsible for the low electrical activation of S implants in GaAs at high dose, and residual surface defects may be a limiting factor at low dose.

Distribution of electrically active Mg implants in GaAs

The electrical properties of Mg‐implanted GaAs have been studied in detail using the van der Pauw technique. Mg ions were implanted in Cr‐doped semi‐insulating GaAs at 120 keV to doses of 1×1013–3×1015/cm2 at room temperature. The implanted samples were annealed with rf‐plasma‐deposited Si3N4 encapsulants at temperatures ranging from 600 to 850u2009°C. p‐type layers have been produced for all dose levels. The maximum electrical activation occurred at an annealing temperature of 750u2009°C for all except the lowest dose of 1×1013/cm2. An electrical‐activation efficiency as high as 85% was obtained for the sample implanted to a dose of 3×1013/cm2 and annealed at 750u2009°C. The dopant profiles were very sensitive to annealing temperature and ion dose, broadening significantly at or above 750u2009°C. Double peaks in the depth profiles have been observed for doses of ?1×1014/cm2, and the maximum carrier concentration obtained was as high as 2×1019/cm3.

Dependence of Anisotropic Strain Relaxation on Composition of Lattice-Mismatched InGaAsP

The strain relaxation behavior of compressively strained InGaAsP grown on InP is studied using double-crystal X-ray diffractometry. The residual strain in compressively strained InGaAsP of various thicknesses follows the half-loop nucleation model. Anisotropic relaxation is observed, and the preferential direction of relaxation is found to change with the composition of InGaAsP. In the quaternary InGaAsP epilayers studied, the relaxation along [110] is larger than that along [110], but the direction is reversed for the ternary InGaAs and InAsP. The change in the direction of the preferential relaxation is thought to be caused by a change in the critical stress and the dislocation velocity as the composition of the epilayer is changed.

Comparative studies of Mg implants in GaAs in different annealing environments

Abstract A detailed electrical measurement study has been carried out for Mg-implanted GaAs using plasma deposited Si 3 N 4 capping, pyrolytic Si 3 N 4 capping, and close-contact capless annealing techniques. Mg ions were implanted in Cr-doped semi-insulating GaAs at 120 keV with doses of 1 × 10 13 to 3 × 10 15 /cm 2 at room temperature. The implanted samples were then annealed at temperatures from 600 to 900°C in flowing hydrogen gas. P-type layers werre produced at all dose levels. Maximum electrical activations occured at 750°C anneal for ion doses ⩾3 × 10 13 /cm 2 , and an activation efficiency of 100% was obtained for a dose of 3 × 10 13 /cm 2 after capless annealing at 750°C for 30 min. The annealing characteristics of surface-carrier concentrations and mobilities obtained by the three capping/annealing methods generally agree for high doses, but there are considerable differences in dopant profiles. Electrical activation was also investigated as a function of annealing time at 750°C. Dopant profiles were very sensitive to ion dose, annealing temperature, and annealing times, and generally showed significant redistribution of Mg ions. Moreover, double-peak structures in the dopant profiles were observed for high doses, and a maximum carrier concentration of 2 × 10 19 /cm 3 was obtained. The capless annealing method used in this study was successful and reproducible.

The role of complementary species in P/Be and Ar/Be co-implanted InP

Chemical and damage effects are used to explain the influence of complementary species on the activation of co-implanted InP. Recently Raoet al. have shown that the damage is the effective mechanism of enhancing activation efficiency and preventing in-diffusion in the P/Be and Ar/Be co-implanted InP. We have confirmed the results and further examined the role of the complementary species by varying their doses. Activation efficiencies as high as 75% and 69.5% were observed in the P/Be and Ar/Be co-implantation, respectively, which can be compared with 31.7% activation in the Be single implantation. Both activation efficiency and in-diffusion decreased as doses of P and Ar increased, that is, as the amount of damage increased. P/Be had always higher activation efficiency than that of Ar/Be when the doses of co-implants are equal. The ratio of the difference in the two activation efficiencies to that of P/Be was the largest at 1014 cm−2 of co-implant dose. This behavior was attributed to the chemical effect of the co-implanted P. Photoluminescence results near the band edge showed that the intensity of the main peaks of Be single implantation decreased with increasing P and Ar doses.

Schottky barrier heights and conduction-band offsets of In1−xGaxAs1−yPy lattice matched to GaAs

The Schottky barrier heights of Au/In1−xGaxAs1−yPy contacts have been determined as a function of y by the capacitance–voltage and temperature dependent current–voltage characteristics measurements. The barrier height is observed to increase as y is increased for both n- and p-type materials, with a more rapid increase for the p-type material. The compositional variation of the barrier heights for Au/n-In1−xGaxAs1−yPy is found to be identical to that of the conduction-band offsets in In1−xGaxAs1−yPy/GaAs heterojunctions. A possible cause of this phenomenon is also discussed.

Photoluminescence due to hole capturing of DX− centers in In0.32Ga0.68P : S

The photoluminescence (PL) characteristics of S-doped In0.32Ga0.68P epilayer grown by liquid phase epitaxy have been studied in the temperature range of 20–300 K. In addition to the two peaks of the near band-edge emission and the donor-to-acceptor transition, a third peak of 2.199 eV at 74 K is observed in a narrow sample temperature range. It is shown that the appearance of this peak is related to the DX centers. The transition is attributed to the recombination of the neutral donor with a hole bound to the DX− center.

Negative Resistance of AlGaAs Diodes Co-doped with Si and Mn

The co-doping effects of Mn on AlGaAs:Si diodes grown by a single-step liquid phase epitaxy (LPE) technique are investigated. Their current-voltage (I-V) characteristics are studied as a function of Mn and Al compositions. It is found that the breakdown voltage and the voltage drop increase with the concentrations of Mn and Al. These results are well explained by the increase of the thickness of the P°-region and the decrease of free hole concentration in its region.