RECOMBINATION CENTERS IN GAAS AL0.4GA0.6AS HETEROSTRUCTURES INVESTIGATED BY OPTICALLY AND ELECTRICALLY DETECTED MAGNETIC-RESONANCE/

Using optically and electrically detected magnetic resonance (ODMR and EDMR, respectively), recombination in a GaAs/Al0.4Ga0.6As heterostruc ture is studied. ODMR performed at 35 GHz shows the presence of Ga int erstitials in a GaAs quantum well codoped with Si and Be. Depending on the contacts used, EDMR (performed both at 9 and 34 GHz) is able to d etect surface defects, intrinsic defects (Ga interstitial and As-Gr an tisite) as well as the Cr4+ transition-metal impurity. The location of the paramagnetic states in the heterostructure was determined with ED MR using light of different absorption length for the selective excita tion of photoconductivity, combined with a phase shift analysis of the different EDMR signals with respect to the modulation reference. The temperature and microwave power dependence of the EDMR signal amplitud e is discussed, providing guidelines for the experimental conditions n eeded to perform EDMR on GaAs. Finally, using X-band and Q-band detect ion, the defect parameters (g-factor and hyperfine constants) for the Ga interstitial an determined to g = 2.006, A(69) = 0.048 cm(-1), and A(71)= 0.061 cm(-1). These results are compared to previous observatio ns.