InP掺杂超晶格的MOCVD生长与表征

用常压MOCVD技术生长了InP掺杂超晶格,所用源材料为TMIn和PH3.InP的载流子浓度低为8×1013cm-3,300K迁移率高达5744cm2/V·s.n型掺杂剂是DETe,p型为DMZn,两者在InP中的掺杂浓度均可达~1019cm-3.用不同激发强度下的低温PL谱,时间衰减,时间分辨PL谱和光反射(PR)谱技术表征了InP掺杂超晶格.文中给出了在不同激发强度下InP掺杂超晶格的4KPL谱,该样品由六层(n·p)组成,每层厚度200Å,掺杂浓度分别是1×1018cm-3和2×1018cm-3.发光峰值能量明显低于InP的禁带宽度,当激发强度增加时峰值能量移向高能边,这是真实空间中的间接跃迁特征.总PL信号衰减分成几步,每步都按指数规律,在4K情况下,衰减常数从6×10-8秒到7×10-4秒,具有明显间接带隙材料特征.InP掺杂超晶格中的量子尺寸效应用PR谱技术进行了研究.为描述InPnipi结构中的量子尺寸效应,引进了抛物型势阱模型,实验结果与根据引进模型所进行的计算相符.

MOCVD GROWTH AND CHARACTERIZATION OF InP DOPING SUPERLATTICES

Doping superlattices (nipi structures) have been grown in InP using organometallic vapor phase epitaxy in an atmospheric pressure reactor using trimethylindium and phosphine. The unintential doping levels in InP employed in these experiments were as low as 8×1013cm-3 and 300K mobilities as high as 5744cm2/V·s. The n- and p- type dopants were diethyltel-lurium and dimethylzinc, respectivly, both n-, p- carrier concentritions can be up to 1019cm-3. Such structures have been characterized using low temperature photoluminescence at various excitation intensities,time decay, time resolved photoluminescence, and photo-reflectance experiments. The 4K photoluminescence spectra at various excitation intensities are presented for a structure consisting of six 200Å layers with doping levels of 1×1018 and 2×1018cm-3 for the n- and p-layers. The luminescence peak is found to occur at energies considerable less the band gap of InP and to move to higher energies with increased excitation intensity, as expected for doping superlattices where the band gap,which is indirect in real space, increases with increasing excited carrier concentration. The total photoluminescence signal decays in several steps, each exponential,with time constants ranging from 6×10-8 to 7×10-4 seconds at 4K.Typical of these spatially indirect band gap materials. Quantum size effects existing in InP doping superlattices have also been probed with photo-reflectance technique. All experimental results are in good agreements with model calculations, which assume a parabolic well to describe the quantum size effects in InP doping superlattices.