Temperature dependence of transport properties of InN films
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0892-FF08-06.1
Temperature dependence of transport properties of InN films J.S. Thakur, 1,* R. Naik,2 V.M. Naik,3 D.Haddad,2 G.W. Auner,1 H. Lu,4 and W.J. Schaff 4 1
Department of Electrical and Computer Engineering, Wayne State University, Detroit, MI 48202 Department of Physics and Astronomy, Wayne State University, Detroit, MI 48202 3 Department of Natural Sciences, University of Michigan-Dearborn, Dearborn, MI 48128 4 Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14583 2
ABSTRACT The temperature dependence of Hall mobility, ยต , and carrier density, N e , for thin InN films grown by Molecular Beam Epitaxy and Plasma Source Molecular Beam Epitaxy have been investigated. For temperature up to 300 K, a large temperature-independent N e is observed in films grown by the above two techniques. However, for higher temperatures, carrier density (Ne) increases with temperature. The characteristic behavior of the mobility for the films with low carrier density is different from that of the high carrier density film, particularly at low temperatures. The low carrier density film shows a peak ~250 K in mobility as a function of temperature which is contrast to the temperature independent mobility observed for the high density film for T < 300 K. We have investigated theoretically the effect of concentration of donor, acceptor, and threading dislocations on the carrier mobility in these films. Various electron-scattering mechanisms for the mobility in these films have been discussed. INTRODUCTION Recently, there has been an extensive revision in the optical,1-3 electrical4 and other properties of InN thin films because of their potential applications in optoelectronic, and for high temperature and high-power electronic device areas. Although many of the InN films properties have been studied since the 1980s, still there are many properties which are not fully understood yet. Recently, many groups have shown that the band gap, Eg, is much smaller (0.65 --0.90 eV)1-2 than conventionally accepted (1.89 to 2.0 eV)5-6 values. The coupled-modes formed by interaction of electrons and LO-phonons are not yet established in InN films.3 Disorder can change qualitatively the optical and other properties of the films.7 Recently, it was found that the surface states formed at a metallic In-clusters/InN interface in the films8 emit a bright infrared light whose low energy (0.7 -- 0.8 eV) matches with the small bandgap values, so this emission has in fact been associated8 with the small bandgap value of the films. On the other hand, the large bandgap values measured in high-density films can be interpreted in terms of the MossBurstein shift.9 Recently, an interesting phenomenon of electron accumulation on InN surfaces was also observed due to surface disorder formed by donor-type resonant surface states.10 EXPERIMENT Samples studied in this work were grown by conventional Molecular Beam Epitaxy (MBE) at Cornell University, and by Plasma Source Molecular Beam Epitaxy (PSMBE) at Wayne State University. In
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