Temperature-dependent photoluminescence(PL) of phase-separated InGaN quantum wells is investigated over a broader excitation power range. With increasing excitation power from 0.5 ^xW to 50 mW, the In-rich quasi-quantum dot(QD)-related PL peak disappears at about 3 mW, while temperature behavior of the InGaN matrix-related PL peak energy(linewidth) gradually evolves from a strong "S-shaped"("W-shaped")temperature dependence into a weak ^S-shaped15(an approximately ￡tV-shaped75), until becoming an inverted"V-shaped"(a monotonically increasing) temperature dependence. This indicates that, with increasing excitation power, the carrier localization effect is gradually reduced and the QD-related transition is submerged by the significantly enhanced InGaN matrix-related transition, while the carrier thermalization effect gradually increases to become predominant at high excitation powers.
Excitation power and temperature-dependent photoluminescence(PL) spectra of the ZnTe epilayer grown on(100)Ga As substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the Ga As substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor–acceptor pair(DAP) nor conduction band-acceptor(e–A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal.
The photoluminescence(PL) properties of a green and blue light-emitting InGaN/GaN multiple quantum well structure with a strong phase separated into quasi-quantum dots(QDs) and an InGaN matrix in the InGaN epilayer are investigated.The excitation power dependences of QD-related green emissions(P_D>) and matrix-related blue emissions(P_M) in the low excitation power range of the PL peak energy and line-width indicate that at 6 K both P_m and P_D are dominated by the combined action of Coulomb screening and localized state filling effect.However,at 300 K,P_m is dominated by the non-radiative recombination of the carriers in the InGaN matrix,while P_D is influenced by the carriers transferred from the shallower QDs to deeper QDs by tunnelling.This is consistent with the excitation power dependence of the PL efficiency for the emission.
