MOCVD生长的GaN:Mg外延膜的光电性质

用MOCVD技术生长GaN:Mg外延膜,在550～950℃温度范围内,对样品进行热退火,并进行室温Hall、光致发光谱(PL)测试.Hall测试结果表明,850℃退火后空穴浓度达到8×1017 cm-3以上,电阻率降到0.8Ω·cm以下.室温PL谱有两个缺陷相关发光峰,位于2.8eV的蓝光峰(BL)以及3.27eV附近的紫外峰(UVL).蓝光峰对紫外峰的相对强度(BL/UVL)在550℃退火后升高,之后随着退火温度的升高(650～850℃)而下降,继续提高退火温度至950℃,BL/UVL急剧上升.空穴浓度先随着Mg掺杂浓度的增加而升高;但继续增加Mg掺杂浓度,空穴浓度反而下降.这些结果表明要实现空穴浓度达1018 cm-3,不仅要考虑H的钝化作用,还要考虑Mg受主的自补偿效应.

Optical and Electrical Properties of GaN: Mg Grown by MOCVD

Mg-doped GaN layers prepared by metalorganic chemical vapor deposition were anealed at temperatures between 550 and 950℃. Room temperature (RT) Hall and photoluminescence (PL) spectroscopy measurements were performed on the as-grown and annealed samples. After annealing at 850℃ ,a high hole concentration of 8×1017 cm-3 and a blue band is centered at 2.8eV (BL) and the ultraviolet emission band is around 3.27eV (UVL). The relative intensity of BL to UVL increases after annealing at 550℃, but decreases when the annealing temperature is raised from 650 to 850℃,and finally increases sharply when the annealing temperature is raised to 950℃. The hole concentration increases with increased Mg doping, and decreases for higher Mg doping concentrations. These results indicate that the difficulties in achieving high hole concentration of 1018 cm-3 appear to be related not only to hydrogen passivation,but also to self-compensation.