部分有序(AlxGa1-x)0.51In0.49P(x=0.29)合金的发光衰退过程

利用时间分辨光谱研究了(Al_xGa_1-x)_0.51In_0.49P合金的时间衰退过程,观察到载流子的转移过程和PL谱峰蓝移现象。这和变温发光谱中谱峰的Z-型依赖关系相吻合。这种现象明显表明了载流子的转移过程和子带的存在,证实了我们对超晶格带折叠效应的猜测。子带是由于有序结构的超晶格效应使导带的L带折叠到Γ带,载流子在时间衰退过程中从Γ带转移到L带。时间分辨光谱的蓝移现象同时也揭示了PL变温谱中谱峰反常蓝移现象的来源。

Luminescence Decay of Partially Ordered ( Alx Ga1 - x ) 0. 51In0. 49P ( x = 0.29 ) Alloy

In this paper, time-resolved photoluminescence(TRPL) was applied to study the optical properties of partially ordered quaternary (Al_xGa_1-x)_0.51In_0.49P(x=0.29) alloy grown by MOVPE, the process of the transfer of carriers and the blue-shift of PL peak in (Al_xGa_1-x)_0.51In_0.49P(x=0.29) alloy are directly observed.Both excitation-wavelength dependence of lifetime and excitation-intensity dependence of lifetime show wide distribution of carriers along bands.In TRPL spectra measured at 77K, the PL peak almost keeps unchanged, while at 300K, the PL peak has a small blue-shift with the delay of time, which is completely opposite to the character of donor-acceptor pair (DAP). The blue-shift phenomenon apparently suggests the occurrence of transfer of carriers and is coincident with the report of the Z-shape character of the PL temperature-dependent spectra, in which an anomalous blue-shift of PL peak energy occurs between 55K and 84K. This phenomenon further indicates the existence of sub-bands which is derived from the superlattice effect of ordered structure, which is a so-called orientational superlattice structure and which is considered to be a composite of the low-band-gap ordered domains in a high-band-gap disordered matrix. Thus, this phenomenon verifies our conjecture about band-folding effect of conduction band from L band to Γ band, i.e., the carriers transfer from Γ band to L band during the decay time. The transfer of carriers between Γ and L band reveals the origin of the anomalous blue-shift in the PL temperature-dependent spectra as well. The single exponential component fitting equation suggests the same category carriers of Γ band and L band. The transfer of carriers at 300K is more apparent than that at 77K. This is because that the blue-shift effect of PL peak energy occurs during 55～84K, the luminescence is dominated by L band at 300K and it is easier for the carriers to get energy to transfer under higher temperature.