Hamburg 2001 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 24: Poster II

HL 24.12: Poster

Donnerstag, 29. März 2001, 10:30–19:00, Rang S\ 3

Compensation Mechanisms in MBE and MOVPE grown GaN — •Helder R. Alves, Dirk Meister, Albrecht Hofstaetter, Detlev M. Hofmann, and Bruno K. Meyer — I. Physics Institute, Justus-Liebig-University Giessen

P-type conduction of GaN is typically obtained by Mg doping which acts as an acceptor. High acceptor concentrations are desirable for many applications but compensation effects limit the achievable free hole concentrations, especially in the samples grown by metal organic vapour phase epitaxy (MOVPE). We studied several series of GaN samples grown by MOVPE and molecular beam epitaxy (MBE)doped with different Mg concentrations by photoluminescence (PL) and Hall measurements. For the MOVPE samples a saturation of the hole density vs the Mg concentration is observed. In the PL spectra of the low doped samples the donor acceptor pair recombination at 3.26 eV is observed, while in the highly doped samples a band at 2.9 eV dominates. In the MBE samples, independent of the Mg concentration, both bands are seen with rather constant intensity ratios and no saturation of the free carrier concentration is observed. Considering the differences in the growth processes like temperature and the presence of hydrogen we formulate a model to explain the compensation mechanism and the nature of the involved defects.