An electrical and photoluminescence study of pseudomorphic GaAs/In 0.11Ga0.89As/Al0.23Ga0.77As HEMT structures

Reports on the variation of the electrical (Hall) and photoluminescence (PL) properties of HEMTs in which either the spacer layer thickness, the AlGaAs doping concentration or the indium mole fraction was varied. All the samples were grown in a V80H MBE system. A standard HEMT structure was chosen which consisted of a 1 μm undoped GaAs buffer layer, 150 Å undoped In_0.11Ga_0.89As layer, 40 Å undoped Al_0.23Ga_0.77As spacer layer, 400 Å 1.5×10¹⁸ cm^-3 silicon doped Al_0.23Ga_0.77As layer and a 100 Å 2×10 ¹⁸ cm^-3 silicon doped GaAs cap layer. The authors list the samples used in this study and shows the variations from the standard structure. Variable temperature Hall measurements were made using indium contacted Van der Pauw samples. Photoluminescence measurements at a temperature of 4 K were carried out at pump powers of 13 mW cm^-2 using the 5145 Å argon ion laser line with detection through a Spex 0.5 M monochromator. The indium mole fraction of 11±1% was determined using Raman spectroscopy on a 2 μm thick InGaAs layer