Donor related deep traps in MOMBE Ga/sub 0.51/In/sub 0.49/P/GaAs heterostructures: influence on the low temperature performance of HEMTs

The authors compare sulfur and silicon doped heterostructures grown by MOMBE (metal-organic molecular-beam epitaxy). High electron mobility transistors (HEMTs) have been fabricated using both S- and Si-doped Ga/sub 0.51/In/sub 0.49/P donor layers. Significant differences between silicon and sulfur doping have been observed using deep-level transient spectroscopy (DLTS) and thermally stimulated capacitance (TSCP). The results of this investigation will allow effective dopant selection and optimized MOMBE growth of Ga/sub 0.51/In/sub 0.49/P/GaAs HEMTs to be carried out. The DLTS studies in Ga/sub 0.51/In/sub 0.49/P/GaAs S- and Si-doped heterostructures indicate the presence of electron traps which have some of the properties of DX centers. These traps, having smaller capture cross section, are less efficient ´Dx-like´ centers in Si-doped samples. They suppress the PPC (persistent photoconductivity) effect and result in more stable low-temperature operation of the HEMT devices.<>