UP-CONVERTED PHOTOLIMINESCENCE IN ORDERED GaInP/GaAs HETEROINTERFACE AND ITS PRESSURE EFFECTS

金属有机气相外延生长的GaInP/GaAs结构的量子阱（QW）发射可以被1.35 ~ 1.46eV的异常带掩盖。我们利用上转换光致发光（UPL）研究了部分有序的GaInP/GaAs量子阱，其中样品发射的光子能量高于激发光子的能量，以及在高于GaInP带隙的光子能量和高压下激发的正常光致发光（PL）。在2.54eV激发下，在两个界面处都有薄GaP层的样品的PL光谱以~ 1.53eV的GaAs QW发射为主。只有一个GaP层的样品的光谱显示没有qw相关的发射，而是在~ 1.46eV处有一个宽峰，在GaAs带边缘有两个弱峰（1.51eV）和一个杂质相关的发射（1.49eV）。通过高压PL测量，1.46eV的峰值可归因于界面附近发生的空间间接跃迁。当光子能量为1.58eV（远低于GaInP带隙而高于GaAs带隙）时，~ 1.46eV的发射带强度急剧下降，而弱的近带边跃迁变得强。此外，所有具有薄GaP层的样品在~ 1.89eV处都显示出UPL。这一能量接近于部分有序GaInP的正常PL。在两层GaP薄层的样品中没有观察到UPL，其中不存在~ 1.46eV的发射。这些结果表明，光生电子在GaInP层中的存在是观测到的1.46eV发射和UPL的主要原因。理论论证表明，随着GaInP层变得更加有序，GaInP和GaAs之间的ii型波段对准。讨论了观测UPL的两步双光子吸收机制。本文观测到的~ 1.46eV发射和UPL都为II型波段对准提供了新的证据。

Quantum well (QW) emission from GaInP/GaAs structures grown by metalorganic vapor phase epitaxy can be masked by anomalous bands at 1.35〜1.46eV. We have studied partially ordered GaInP/GaAs QWs using up-converted photoluminescence (UPL) in which a sample emits photons with an energy higher than that of the excitation photon, together with the normal photoluminescence (PL) excited at a photon energy higher than that of the GaInP band gap and at high pressures.Using 2.54eV excitation the PL spectra from the sample with a thin GaP layer at both interfaces is dominated by the GaAs QW emission at 〜1.53eV. Spectra from the samples with only one GaP layer show no QW-related emission, instead a broad peak at 〜1.46eV and two weak peaks from the GaAs band-edge (1.51eV) and an impurity-related emission (1.49eV) are observed. Using high-pressure PL measurements, the 1.46eV peak can be attributed to spatially indirect transitions occurring in the vicinity of the interface. When excited with a photon energy of 1.58eV, which is well below the GaInP band gap but above the GaAs band gap, the 〜1.46eV emission band shows a drastic decrease in intensity while the weak near band-edge transitions become strong. In addition, all the samples with a thin GaP layer show UPL at 〜1.89eV. This energy is close to that of the normal PL of partially ordered GaInP. No UPL can be observed in the sample with two thin GaP layers, where the 〜1.46eV emission is absent. These results suggest that the presence of photo-generated electrons in the GaInP layer is greatly responsible for the observed 1.46eV emission and UPL.Theoretical arguments have suggested a type-II band alignment between GaInP and GaAs as the GaInP layer becomes more ordered. A two-step two-photon absorption mechanism for observing UPL has been discussed. Both the 〜1.46eV emission and the UPL observed in this work provide new evidence of a type II band alignment.