Search

The results of self-heating simulations of the GaN-based metal-oxide-semiconductor high electron-mobility transistors (MOS-HEMTs), including hot electron and quantum effects are reported using two-dimensional numerical simulator. Results reveal that the presence of the interface charges and traps are directly responsible for the observed current collapse and device switching in the GaN-based MOS-HEMTs.

Abstract: Piezomodulated reflectance (PzR) spectroscopy has been used to study the InAs/In0.15Ga0.85As quantum dots-in-a-well (DWELL) samples in the temperature range of 70–300K. The optical transitions from ground state to excited states in InAs DWELL were observed. The heavy- and light-hole transitions from the hybrid quantum well (HQW) were identified by combining the one-dimensional effective mass approximation (EMA) with the selected modulation effect in PzR spectrum. A remarkable red shift of the ground state has been observed in the InAs DWELL with optimized growth of In0.15Ga0.85As quantum well layers. Cooling both DWELL samples produces an abnormal broadening of the QD transitions in PzR spectra. [Copyright &y& Elsevier]

Abstract: Piezomodulated reflectance (PzR) spectra at 77 and 300K have been measured for InAs/In0.15Ga0.85As dots-in-a-well and a conventional InAs/GaAs quantum dots. The optical features of both samples were well resolved and confirmed by photoluminescence results. Numerical calculations are in good agreement with the experimental results. The transitions in sandwiched structure formed by InAs wetting layer and In0.15Ga0.85As/GaAs quantum well supports the model of strain-driven alloy decomposition. The abnormal intensity between heavy-hole-type and light-hole-type transition of such sandwiched structure in PzR spectra has been discussed in terms of increased hydrostatic strain in In0.15Ga0.85As/GaAs quantum well. [Copyright &y& Elsevier]

Abstract: Signatures associated with electronic states confined in two strained In x Ga1–x As/GaAs single quantum wells have been observed in its piezomodulated (PzR) and photomodulated (PR) reflectivity spectra. One comparison of the relative intensity between 11H and 11L signatures in PzR of GaAs/In0.14Ga0.86As SQW emphasizes the contribution of strain dependence of energies of the confined states; the other comparison of corresponding confined states between PzR and PR spectra in both samples has been introduced to interpret the discrepancy of the relative intensity in term of modulated strength, and the calculated ratio of energy shifts induced by strain to that of produced by surface electric field agree with the experimental observation. [Copyright &y& Elsevier]