P- and N-Type Doping of MBE Grown Cubic GaN/GaAs Epilayers
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D.J. As,* T. Simonsmeier, * J. Busch,* B. Sch6ttker,* M. Luibbers,* J. Mimkes,* D. Schikora,* K. Lischka,* W. Kriegseis,** W. Burkhardt,** B.K. Meyer** Universitit Paderborn, FB-6 Physik, Warburger StraBe 100, D-33095 Paderborn, Germany, [email protected] •* Universitdit Giessen, I. Physik. Inst. , Heinrich-Buff-Ring 16, D-35392 Giessen, Germany *
Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G 3.24 (1999) ABSTRACT P-type doping with Mg and n-type doping with Si of cubic GaN (c-GaN) epilayers is reported. Cubic GaN films are grown by if-plasma assisted MBE on semi-insulating GaAs (001) substrates at a substrate temperature of 720'C. Elemental Mg and Si are evaporated from thermal effusions cells. Secondary ion mass spectroscopy (SIMS), low temperature photoluminescence (PL) and temperature dependent Hall-effect measurements are used to study the incorporation, optical and electrical properties. A Mg related shallow donoracceptor transiton at 3.04 eV with an acceptor activation energy of EA= 0.230 eV is observed by low temperature PL. At Mg concentrations above 1018 cm-' the dominance of a broad blue band indicates that also in c-GaN Mg is incorporated at different lattice sites or forms complexes. Si-doped c-GaN epilayers are n-type with electron concentrations up to 5*10 19 cm. The incorporation of Si follows exactly the vapor pressure curve of Si, indicating a sticking coefficient of I for Si in c-GaN. With increasing Si-concentration the intensity of the near-band luminescence continuously increases and broadens.
INTRODUCTION Cubic GaN (c-GaN) epilayers grown by molecular beam epitaxy (MBE) show outstanding electrical and optical features [1,2], demonstrating the high potential of c-GaN for the realization of blue emitting laser diodes. Gain measurements in undoped cubic material reveal gain values which are comparable to that of the best hexagonal GaN (hGaN) [3]. Particularly, epitaxially grown layers of c-GaN lend themselves to the production of cleaved laser cavities and optically excited stimulated emission from such cleaved facetts has already been observed [4]. In order to fabricate almost any device it is necessary to carry out controlled doping of GaN in order to realize both n-type and p-type GaN material. In hexagonal GaN the principal p-type dopant is Mg and n-type dopant is Si. In this paper we summarize recent doping experiments of cubic GaN epilayers by Mg and Si. Secondary ion mass spectroscopy (SIMS), low temperature photoluminescence (PL) and temperature dependent Hall-effect measurements are used to study the incorporation, the optical and electrical properties of Mg- and Si-doped samples.
G 3.24 Mat. Res. Soc. Symp. Proc. Vol. 537 © 1999 Materials Research Society
EXPERIMENTAL Cubic GaN films are grown by if-plasma assisted MBE on semi-insulating GaAs (001) substrates at a substrate temperature of 720'C. The growth rate is about 0.07 ltm/h and the thickness of the layers is about 1 pm, respectively. Elemental Mg and Si are evaporated from commercial effusion cells
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