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

用金属有机物气相外延生长的GaInP/GaAs结构的量子阱（QW）发射可以被1.35 ~ 1.46eV的反常带所掩盖。我们利用上转换光致发光（UPL）研究了部分有序GaInP/GaAs量子阱，与正常的光致发光（PL）一起，在高于GaInP带隙的光子能量和高压下激发。使用2.54eV激发，来自在两个界面处具有薄GaP层的样品的PL光谱由GaAs量子阱发射在1.53eV处。只有一个GaP层的样品的光谱没有显示出量子阱相关的发射，而是观察到在1.46eV处的宽峰和来自GaAs带边的两个弱峰（1.51eV）和杂质相关的发射（1.49eV）。使用高压PL测量，1.46eV的峰值可以归因于发生在界面附近的空间间接跃迁。当用1.58eV的光子能量激发时，这远低于GaInP的带隙，但高于GaAs的带隙，1.46eV的发射带显示出强度急剧下降，而弱的近带边跃迁变得强烈。此外，所有具有薄GaP层的样品都显示出在1.89eV处的UPL。这一能量接近部分有序GaInP的正常PL的能量。在具有两个薄GaP层的样品中没有观察到UPL，其中没有1.46eV的发射。这些结果表明，GaInP层中光生电子的存在是导致1.46eV发射和UPL的主要原因。理论分析表明，随着GaInP层的有序化，GaInP和GaAs之间的能带排列呈现II型。本文讨论了观察UPL的两步双光子吸收机制。在这项工作中观察到的1.46eV发射和UPL提供了II型带排列的新证据。

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.