The Effect of Low Temperature GaAs Nucleation on the Growth of GaN on Silicon (001) During MOVPE Process
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ABSTRACT High quality cubic GaN was grown on Silicon (001) by metalorganic vapor phase epitaxy (MOVPE) using a GaAs nucleation layer grown at low temperature. The influence of various nucleation conditions on the GaN epilayers' quality was investigated. We found that the GaAs nucleation layer grown by atomic layer epitaxy (ALE) could improve the quality of GaN films by depressing the formation of mixed phase. Photoluminescence (PL) and X-ray diffraction were used to characterize the properties of GaN epilayers. High quality GaN epilayers with PL full width at half maximum (FWHM) of 130meV at room temperature and X-ray FWHM of 70 arc-min were obtained by using 10-20nm GaAs nucleation layer grown by ALE. INTRODUCTION Recent progress in the study of hexagonal structure GaN have attracted much attention to the GaN-based materials. Not only light emitting diodes (LEDs)[1' 21 but also laser diodes (LDs)[31 were successfully fabricated, and the life time of a LD fabricated on sapphire substrate exceeded 10,000 h6urs[4 ]. On the other hand, the research of cubic GaN has lagged behind because of lacking suitable substrate. However, n and p doping are expected to be easy achieved for cubic GaN[51 .The research of cubic GaN possesses both fundamental and applied interests. Many research groups have studied the growth and characterization of cubic GaN using metalorganic vapor phase epitaxy 6 9 0
(MOVPE)' "', molecular beam epitaxy(MBE)' " ' and other growth techniques. Various substrates such as 3C-SiC[1", MgO1121, GaAs[ 69'] and Si1l°] were used. Among these substrates, GaAs and Si are prefered because they are well developed and commercially available. In addition, the p-type cubic GaN films on GaAs have been obtained•' 3 ' 1 . Replacement of sapphire or SiC substrates by silicon would be of great interest for integration of optoelectronics into existing silicon technology. However GaN does not wet Si substrate and the 17% lattice mismatch makes the GaN growth on Si very difficult. Furthermore, during the nitridation step which is normally used for the growth of GaN on sapphire or other substrates, an amorphous silicon nitride film is easily formed, and thus leads to an amorphous or polycrystalline GaN film. However, high quality GaAs epilayers have been grown on Si. We have used a thin GaAs layer grown at low temperature as a nucleation layer on Si and reported a high quality GaAs layer with X-ray rocking curve FWHM of 116 arc-sec and a GaAs/GaAlAs laser diode operating in pulsed mode1 [11,16] . The wurtzitic GaN/InGaN layers were also grown by using a GaAs/Si(l 11) composite substrate117 . In this paper, we report recent results on the growth of cubic GaN epilayers on silicon (001) substrate using a GaAs nucleation layer. The GaAs nucleation layer grown at low temperature could fully cover the Si substrate and supply a cubic nucleation template. The X-ray 0o scan FWHM of cubic GaN epilayers is typically 70 arc-min and PL FWHM at room temperature is 130meV. 69 Mat. Res. Soc. Symp. Proc. Vol. 482 ©1998 Materials Research So
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