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We have demonstrated experimental evidence of non-resonant tunneling at room temperature in GaAs/AlGaAs asymmetric coupled double quantum wells (ACDQW’s) using time-resolved photoluminescence (TRPL) spectroscopy at 300 K. Two ACDQW samples (A and B) with a barrier thickness of 25 A were grown via molecular beam epitaxy. The energy separation (ΔE) between the ground state of the conduction band of the wide well and that of the narrow well are 42.7 meV and 19.5 meV, for samples A and B respectively. The TRPL measurement revealed a double decay rate in sample A whose ΔE is greater than one GaAs longitudinal optical phonon energy (36 meV), suggesting a phonon assisted tunneling mechanism. The evidence of tunneling was supported by measuring the relative intensity of the PL contributions from the narrow and wide well at 10 K.

We investigate the effects of an externally applied magnetic field on the terahertz (THz) emission of Gallium Manganese Arsenide (GaMnAs) films grown via molecular beam epitaxy (MBE). Results show that low Mn-doping in GaMnAs resulted to increased THz emission as compared with a SI-GaAs substrate. Further increase in Mn-doping content resulted to a comparably less THz emission, which is attributed to reduced crystallinity and higher free-carrier absorption. Under an external magnetic field, the contributions of the B u p and B d o w n -related THz emission were observed to be asymmetric: possibly due to intrinsic magnetic properties of GaMnAs.

This study presents the terahertz (THz) emission of molecular beam epitaxy (MBE)-grown Gallium Arsenide (GaAs) on surface textured p-type Silicon (p- Si) (100) substrates. Surface texturing was achieved by anisotropic wet chemical etching using 5% wt Potassium Hydroxide (KOH): Isopropyl alcohol (IPA) (50:1) solution for 15, 30, 45, and 60 minutes. Reflectivity measurements for the textured p-Si(100) substrates indicated that the overall texturing increases with longer etching times. Raman spectroscopy of the post-growth samples confirmed GaAs growth. The THz emission intensities were the same order of magnitude. The GaAs grown on p-Si(100) textured for 60 minutes exhibited the most intense THz emission attributed to the increased absorption from a larger surface-to-volume ratio due to surface texturing. All GaAs on textured p-Si(100) samples had frequency bandwidth of ~2.5 THz.

We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics of the THz signal. The InAs QDs was grown using standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- and 910 nm-wavelength were used to distinguish THz emission from the InAs/GaAs matrix and InAs respectively. THz-TDS at 800 nm pump revealed intense THz emission comparable to a bulk p-InAs. For 910 nm pump, the THz emission generally weakened and upon applying external magnetic field of opposite polarities, the THz time-domain plot exhibited anomalous phase-shifting. This was attributed to the possible current-surge associated with the permanent dipole in the QD.

Low temperature photoluminescence and reflectance measurements on epitaxially lifted-off (ELO) bulk GaAs and GaAs/AlGaAs multiple quantum wells (MQWs) bonded to Si and MgO substrates are reported. Photoluminescence measurements indicate no strain at room temperature for the ELO bulk GaAs film but show biaxial strain at 10 K. Si-bonded films undergo tensile strain, while films with MgO host substrates experience compressive strain. Reflectance measurements at 10 K show that light hole band is closer to the conduction band for the tensile strained film. In GaAs MQW ELO films, the separation of the heavy hole and light hole band is reduced in tensile strained films by 4.7 meV, corresponding to a strain e=−0.7±0.05×10−3 and stress X=0.9±0.05 kbar (90±5 MPa). For compressively strained films, this separation is enhanced by 3.9 meV, equivalent to a strain e=0.6±0.05×10−3 and X=0.8±0.05×10−3 kbar (80±5 MPa). The findings demonstrate that ELO is an effective technique to introduce tensile and compressive strain i...