Pressure Dependence of the Electronic Subband Structure of Strained In_0.2Ga_0.8As/GaAs MQWs

Abstract

We have measured low-temperature photoluminescence (PL) and optical absorption spectra of an Ino,zG~.8As/GaAs multiple quantum well (MQW) structure at pressures up to 8 GPa. Below 4.9 GPa, PL shows only the emission of the n = 1 heavy-hole (HH) exciton. Three new X-related PL bands appear at higher pressures. They are assigned to spatially indirect (type-11) and direct (type-I) transitions from Xz states in GaAs and X X~ valleys of InGaAs, respectively, to the HH subband of the wells. From the PL data we obtain a valence band offset of 80 meV for the strained Ino.zG% &s/GaAs MQW system. Absorption spectra show three features corresponding to direct exciton transitions in the quantum wells. In the pressure range of 4.5 to 5.5 GPa an additional pronounced feature is apparent in absorption, which is attributed to the pseudo-direct transition between a HH subband and the folded Xz states of the wells. This gives the first clear evidence for an enhanced strength of indirect optical transitions due to the breakdown of translational invariance at the heterointerfaces in MQWs.

Photoluminescence Studies on Self-Organized InAlAs/AlGaAs Quantum Dots under Pressure

“…The QD PL shows an initial shift of 90 meV/GPa up to 0.8 GPa, no significant shift (or a small negative shift) between 0.8 and 2.2 GPa, and a decrease in the PL peak energy reminiscent of anti-crossing of energy levels until the PL completely quenches at 2.6 GPa. This pressure behavior is quite interesting and different from that reported for InAs/GaAs QD [5], or InGaAs/GaAs [6,7] and InGaAs/AlGaAs [8,9] strained layer quantum wells. Fig.…”

Photoluminescence Studies on Self-Organized InAlAs/AlGaAs Quantum Dots under Pressure

“…The QD PL shows an initial shift of 90 meV/GPa up to 0.8 GPa, no significant shift (or a small negative shift) between 0.8 and 2.2 GPa, and a decrease in the PL peak energy reminiscent of anti-crossing of energy levels until the PL completely quenches at 2.6 GPa. This pressure behavior is quite interesting and different from that reported for InAs/GaAs QD [5], or InGaAs/GaAs [6,7] and InGaAs/AlGaAs [8,9] strained layer quantum wells. Photoluminescence Studies on InAlAs/AlGaAs Quantum Dots under Pressure 87 3 The GaAs PL overlaps with the QD PL for P b 2 GPa, but its linewidth is quite narrow and hence the error in the FWHM of the QD PL is`5% above 2 GPa.…”

“…As pressure increases further, there is yet another crossover between the G confined level and X z or the barrier X band around 2.6 GPa. The mixing of these bands causes an anticrossing behavior in the vicinity of the crossover pressure similar to that reported in the InAs/GaAs QD grown on misoriented substrate [7]. After the crossover, the type-II QD PL is undetectable because the transition is indirect in both real and k-space.…”