ENERGY-DEPENDENCE AND DEPTH DISTRIBUTION OF ELECTRON-BEAM-INDUCED DAMAGE IN GAAS/ALGAAS HETEROSTRUCTURES

We have investigated the effects of electron beam (EB) irradiation on the optical and electrical properties of GaAs/AlGaAs heterostructures in the energy range between 5 and 25 keV and at electron doses of 1 x 10(16) approximately 1 x 10(21) electrons/cm2. The most pronounced effects were observed for 10 keV EB irradiation. The photoluminescence (PL) intensity from quantum wells and the two-dimensional-electron-gas (2DEG) mobility were reduced at doses greater than 1 x 10(19) electrons/cm2 and 5 x 10(20) electronS/cm2, respectively. On the other hand, for 5 and 25 keV, those degradations were not observed. For various EB energies, the depth distribution of EB-induced damage was determined by both PL and 2DEG mobility measurements. Using a Monte-Carlo simulation, the damage distribution was shown to be correlated with the energy-loss distribution of incident electrons. Namely, the penetration of 5 keV electrons is too shallow to cause any damage in the active region at around 100 nm depth. On the other hand, since the energy-loss distribution of 25 keV electrons is too broad and deep due to the reduced cross section of collisions between the electrons and target, it has little effect on the photoluminescence (PL) and the 2DEG mobility. Consequently, 10 keV electrons lose most of their energy in the active region (100 nm depth), being consistent with the observed degradation of the PL and 2DEG mobility.