Electrical Properties of Cubic InN and GaN Epitaxial Layers as a Function of Temperature
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Instituto de Física da USP, C.P. 66318, 05315-970 São Paulo, SP, Brazil, [email protected] ** Universidade São Francisco, Centro de Ciências Exatas e Tecnológicas, 13251-900 Itatiba, SP, Brazil *** Instituto Nacional de Pesquisas Espaciais (INPE-LAS), C.P. 515, 12201-970 São José do Campos, SP, Brazil **** Universität Paderborn, FB-6 Physik, Warburger Strasse 100, D-33095 Paderborn, Germany Cite this article as: MRS internet J. Nitride Semicond. Res. 595, W3-40 (2000). ABSTRACT Carrier concentration and mobility were measured for intrinsic cubic InN and GaN, and for Si-doped cubic GaN as a function of temperature. Metallic n-type conductivity was found for the InN, while background p-type conductivity was observed for the intrinsic GaN layer. Doping the cubic GaN with Si two regimes were observed. For low Si-doping concentrations, the samples remain p-type. Increasing the Si-doping level, the background acceptors are compensated and the samples became highly degenerated n-type. From the carrier concentration dependence on temperature, the activation energy of the donor and acceptor levels was determined. Attempts were made to determine the scattering mechanisms responsible for the behavior of the mobility as a function of temperature. INTRODUCTION In the past few years nitride-based nanostructures have been successfully used in the fabrication of optoelectronic devices as well as in the development of high frequency and high-temperature electronic devices [1-4]. Most of the applications made so far are based on the hexagonal (h) phase of the nitride materials. However, cubic (c) GaN/GaAs (001) layers grown by metal organic chemical vapor deposition (MOCVD) and by plasma assisted molecular beam epitaxy (MBE) have recently been used to fabricate p-n junction light emitting diodes [5-6]. In order to improve on the performance of these devices, further studies of the optical and electrical properties of the nitride layers are required. Particularly, the improvement of the n- and p-type doping levels and carrier mobilities in these layers is a crucial task for the device technology, mainly for that involving the cubic phase of the materials [7,8]. In the present work measurements of carrier concentrations and mobilities of unintentionally doped c-InN and c-GaN MBE grown epitaxial layers are performed as a function of temperature. c-GaN samples doped with silicon are also investigated in the temperatures range 10 to 350K. The carrier concentrations and mobilities obtained for the
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cubic (zinc-blend) InN and GaN layers are compared with the results available for the corresponding hexagonal (wurtzite) nitride samples. SAMPLES The c-InN sample was grown on GaAs/InAs buffer layers firstly grown on GaAs (001) substrate by plasma-assisted MBE. We have used a Riber 32-system equipped with elemental sources of Ga, As, In, Si and an Oxford Research CARS25 radio frequency plasma source for the reactive nitrogen. After the growth of the GaAs buffer layer at a temperature of 610oC, we grew a 300nm layer of InAs at
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