C. H. Lam

Bio: C. H. Lam is an academic researcher from University of Hong Kong. The author has contributed to research in topics: Vacancy defect & Positron Lifetime Spectroscopy. The author has an hindex of 1, co-authored 1 publications receiving 21 citations.

Gallium vacancy and the residual acceptor in undoped GaSb studied by positron lifetime spectroscopy and photoluminescence

Abstract: Positron lifetime, photoluminescence (PL), and Hall measurements were performed to study undoped p-type gallium antimonide materials. A 314 ps positron lifetime component was attributed to Ga vacancy (V-Ga) related defect. Isochronal annealing studies showed at 300 degreesC annealing, the 314 ps positron lifetime component and the two observed PL signals (777 and 797 meV) disappeared, which gave clear and strong evidence for their correlation. However, the hole concentration (similar to2x10(17) cm(-3)) was observed to be independent of the annealing temperature. Although the residual acceptor is generally related to the V-Ga defect, at least for cases with annealing temperatures above 300 degreesC, V-Ga is not the acceptor responsible for the p-type conduction. (C) 2002 American Institute of Physics.

Nature of the acceptor responsible for p-type conduction in liquid encapsulated Czochralski-grown undoped gallium antimonide

Abstract: Acceptors in liquid encapsulated Czochralski-grown undoped gallium antimonide (GaSb) were studied by temperature dependent Hall measurement and positron lifetime spectroscopy (PLS). Because of its high concentration and low ionization energy, a level at EV+34meV is found to be the important acceptor responsible for the p-type conduction of the samples. Two different kinds of VGa-related defects (lifetimes of 280ps and 315ps, respectively) having different microstructures were characterized by PLS. By comparing their annealing behaviors and charge state occupancies, the EV+34meV level could not be related to the two VGa-related defects.

The intrinsic relationship between the kink-and-tail and box-shaped zinc diffusion profiles in n-GaSb

Abstract: Different diffusion sources were used to study Zn diffusion in n-GaSb. We found that the Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface diffusion fronts in Zn profiles, thus converting the kink-and-tail-shaped profile to the box-shaped profile. Our analysis demonstrated that both the surface and the tail regions in the kink-and-tail profiles showed high-quality regularities. The analysis also revealed that the formation mechanism of the box profiles is the same as that of the tail region of the kink-and-tail profiles. The similarities of the photoluminescence signals between the main region of the box profiles and the tail region of the kink-and-tail profiles substantiated our findings.

Native defects and self-diffusion in GaSb

Abstract: The recent results for the self-diffusivities, D(Ga) and D(Sb), of Ga and Sb in GaSb obtained by Bracht et al (Bracht H, Nicols S P, Walukjewicz W, Silveira J P, Briones F and Haller E E 2000 Nature 408 69 and Bracht H, Nicols S P, Haller E E, Silveira J P and Briones F 2001 J. Appl. Phys. 89 5393) are compared and related to the earlier measurements by Weiler and Mehrer (Weiler D and Mehrer H 1984 Phil. Mag. A 49 309). It is proposed that the differences between the two sets of data are due to higher concentrations of hydrogen impurity in the samples of Weiler and Mehrer. The experimental evidence indicates that the diffusion mechanisms associated with D(Ga) and D(Sb) both have two parallel mechanisms. For D(Ga) the native defects involved are the Frenkel pair, GaiVGa, and the Ga vacancy, VGa. For D(Sb) one mechanism is due to the defect pair SbiVGa and the second to either the vacancy pair VGaVSb or the triple defect VGaGaSbVGa. It is proposed that the mobilities of all these defects, excepting GaiVGa, are enhanced in the presence of hydrogen as an impurity in the GaSb lattice. On this basis the differences in the data obtained by Bracht et al and Weiler and Mehrer can be reconciled. It is also shown that measured free hole concentrations identify Ga2−Sb as the residual acceptor in GaSb and that undoped GaSb is intrinsic at diffusion anneal temperatures.