SIGNIFICANCE OF DX-CENTERS FOR ACOUSTIC INDUCED RECONSTRUCTION PROCESSES OF DEFECTS IN GaN/AlGaN

Abstract

The experimental results of amplitude effects are compared (from an ultrasonic wave deformation amplitude – a tension τUS) for electron concentration and changes of the lattice parameter on the same sample GaN/Al0.2Ga0.8N/GaN/AlN. It has been experimentally established that at ultrasonic loading (frequency 5–10 MHz, amplitude – towards 2·104 W/m2) there is a nonlinear increase in the effective electron concentration and an increase in the lattice parameter; at the same time, the mobility of electrons decreases and μН(τUS) ~ |τUS|. The energy parameters of the acoustic activation charge carriers process are calculated from the approximation of experimental amplitude changes – Еа ≈ 50 meV and γn(300 K) ≈ 2,5·10-27 m3. The amplitude dependences (increase) of the relative lattice parameter change (ΔС/С) from the tension τUS have been investigated experimentally at different frequencies. The energy of DX-center transition UDX ≈ 108 meV and the activation volume of this transition γDX ≈ 6,6·10-27 m3 are calculated from the approximation of the experimental amplitude changes. The revealed correlation of the magnitude of acoustic induced effects in different experiments allows to build a quantitative energy model of the acoustic action process based on the properties of metastable DX centers. It is shown that the acoustic induced process occurs due to the dimensional displacement of the DX-center atom (a background impurity of silicon atoms) from the non-central position to the centrally symmetric one; herewith DX-center is ionized, one goes into the d0-state. It is believed that the changes are most likely to occur near penetrating dislocations in the barrier layer Al0.2Ga0.8N – acoustic modulated oscillations of the distance between the possible positions of the donor atom lead to a decrease in the barrier to the displacement of the defect.