Doping of III–V compound semiconductors by ion implantation

Mg+ and As+ ions were implanted into GaAs to study the effects of dual implantation on the electrical properties. Increased electrical activity and significantly less redistribution of the magnesium were observed for the dual implants compared with the single implants. A maximum activity of 40% with a sheet resistivity as low as 185 Ω/⧠ was obtained for the dual implant compared to an activity of 27% with a resistivity of 250 Ω/⧠ for the single implant at a dose of 1015 cm−2. A peak hole concentration approaching 4×1019 cm−3 was recorded for the dual implant annealed at 900 °C for 30 s.

Rapid thermal annealing of Mg++As+ dual 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.

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

The activation of high dose Mg+ implants (1×1015 cm−2, 100 keV) in GaAs using capless rapid thermal annealing has been improved by the co‐implantation of As+. This technique reduces the outdiffusion of the implanted Mg, which can adversely affect the activation of shallow, high dose implants. Compared with an activation of 18% for an implant of Mg+ only, the co‐implantation of As+ has increased the activation to as much as 61% with concomitant sheet resistance of 136 Ω/⧠. The placement of the As+ implant with respect to the position of the Mg+ profile has been determined to play a role in the activation efficiency. This technique has been applied to the formation of thick p+ regions with high surface carrier concentrations, which has important applications in device fabrication for reduction of contact resistances.

Improved activation of Mg+ and As+ dual implants in GaAs by capless rapid thermal annealing

Photoluminescence measurements were made to study the behavior of Mg implants in InP. Mg ions were implanted at an energy of 120 keV into vapor phase epitaxial (VPE) and Fe‐doped, semi‐insulating (SI) InP at doses of 1×1012–1×1015 cm−2 at room temperature. Encapsulation was with Si3N4 followed by face‐down annealing for 15 min at temperatures from 500 to 800 °C. Changes in excitation intensity, temperature, and dosage resulted in the identification of the Mg‐related free‐to‐acceptor and donor‐to‐acceptor transitions where the Mg ionization energy was calculated to be 39.4 meV. Annealing in the 700 and 800 °C range proved sufficient in moving impurities into substitutional sites and making the implants optically active. Activation, which is strongly dosage dependent, was optimum at an anneal temperature of 750 °C for VPE material, while for SI InP, maximum activation was achieved at 800 °C. A broad, structured emission between 1.20 and 1.38 eV was observed for anneal temperatures of 600 and 700 °C; it disa...

Photoluminescence from Mg‐implanted, epitaxial, and semi‐insulating InP

Mg ions were implanted in Cr‐doped semi‐insulating GaAs at 120 keV to doses of 3×1012 to 1×1015/cm2 at room temperature. Surface‐carrier concentrations and mobilities have been measured at various postimplantation anneal temperatures using the van der Pauw Hall‐effect/sheet‐resistivity technique. Detailed profiles of depth as a function of ion dose and anneal temperature are presented. Also, the results of a study of the integrated intensity of Mg emission at various annealing temperatures and of depth profiles of the relative emission intensity of the ions obtained by the photoluminescence method are compared with results obtained from electrical measurements. In addition, compensation‐level analysis and a comparison of theoretical diffusion profiles with depth‐profile data have been made. p‐type layers have been produced for all except the lowest dose of 3×1012/cm2 after capping only (no postimplantation annealing) with pyrolytic Si3N4 encapsulants. Subsequent annealing up to 600 °C does not alter the e...

Y. K. Yeo

Papers

Electrical measurements and optical activation studies in Mg‐implanted GaAs