The MOCVD growth of silicon doped n-type GaN on (0001)-oriented sapphire is reported. At least in the range of 10~(17)-10~(20)cm~(-3), the carrier concentration is sensiblv proportional to the Si/Ga mole fraction ratio. The mobility increases from 100 cm~2/V.s at 10~(20) cm~(-3) to over 200 cm~2/V.s at 10~(18)cm~(-3). The decrease in mobility at low carrier concentrations observed in this study is ascribed to the presence of unidentified impurities in starting reagents. The material becomes degenerate at approximately 10~(19)cm~(-3) as evidenced by a shift in the optical energy gap.
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