UP-CONVERTED PHOTOLUMINESCENCE IN ORDERED AlGaInP ALLOY SEMICONDUCTOR SESTEMS AND ITS PRESSURE EFFECTS

Ga_<0.5>In_<0.5>P在适当条件下生长在GaAs衬底上可以形成自然有序的CuPt超晶格结构。虽然界面在有序结构的形成中起着重要的作用，但由于在生长样品中探测异质界面的困难，对它知之甚少。我们在GaAs衬底上生长的部分有序GaInP外延层和GaAs/GaInP量子阱结构中观察到了GaInP在-1.9eV处的光致发光上转换，（1.58 eV）充分低于GaInP的带隙，但略高于GaAs的带隙（接近1.5 eV）。位置与能量为2.54eV的光子激发的正常光致发光谱的位置接近，但有些谱线形状与正常光致发光谱的谱线形状有很大不同。由于这种上转换过程发生在界面附近，它可以用来探测异质结的性质，如能带偏移和载流子在界面上的扩散。在II型GaAs/部分有序GaInP界面的双光子吸收机制似乎可以解释我们的结果。此外，我们还研究了GaAs/部分有序GaInP量子威尔斯阱中的时间分辨光致发光，这是探测界面的另一种方法。这些结构中的一些在GaInP和GaAs层之间包含GaP的薄（~ 2nm）层。在-1.46 eV处的所谓的“深发射”带占主导地位。这种深发射与GaInP中观察到的有序-无序现象密切相关，提出了一个无GaP层界面处电子和空穴空间间接复合的模型来解释我们的结果，其中GaAs/部分有序GaInP的导带排列为II型.

Ga_<0.5>In_<0.5>P grown on GaAs substrates under appropriate conditions is known to form naturally ordered superlattices with the CuPt structure. Although the interface plays an important role in the formation of the ordered structure, little is known about it due to difficulties in probing the heterointerface in as grown samples. We have observed upconversion of photoluminescence (PL) from GaInP at -1.9 eV in several partially ordered GaInP epilayers grown on GaAs and in GaAs/GaInP quantum well structures when the excitation photon energy (1.58 eV) is sufficiently below that of GaInP but is slightly above the bandgap of GaAs near 1.5 eV.While the spectral" positions are almost close to those of the normal PL excited by photons with energy of 2.54 eV, some of their spectral shapes are quite different from those of normal PL spectra. Since this upconversion process occurs in the vicinity of the interface, it can be used to probe properties of the heterojunction such as the band offsets and diffusion of carriers across the interface. A two-photon absorption mechanism at the type II GaAs/partially ordered GaInP interface seems to explain our results. Also, we have studied the time-resolved photoluminescence in GaAs/partially ordered GaInP quantum wells, which is an alternative way of probing the interfaces. Some of these structures contain thin (- 2 nm) layers of GaP between the GaInP and GaAs layers. A so-called "deep emission" band at -1.46 eV is dominated. This deep emission is closely related to the order-disorder phenomenon observed previously for GaInP.A model for spatially indirect recombinations of electron and holes at the interface without GaP layer is proposed to explain our results, in which the conduction band alignment at the GaAs/partially ordered GaInP is of type II.