Study of trap levels in β-Ga2O3 by thermoluminescence spectroscopy

Abstract

Electronic defects with shallow and deep levels in β-Ga2O3 single crystals were investigated by thermoluminescence (TL) spectroscopy. Undoped, Fe-doped, Sn-doped, and Mg-doped β-Ga2O3 single crystals grown by different methods were studied, and thermal activation energies of defects were calculated using the initial rise method. Hall-effect measurements and optical absorption spectroscopy were performed to determine the electrical transport properties and optical bandgaps. It was found that the dopants do not have any effect on the bandgap energy, which is important for comparing the trap levels in the samples. Three deep trap levels were found in the undoped crystals; the activation energy, ED, and concentration of defect centers for all of them have slightly changed after doping with Fe and Mg. Fe doping induced an additional defect center with activation energy of 0.62 eV. The measurements revealed the absence of TL emission in Sn doped crystals indicating that Sn doping may quench luminescence centers or modified some original electronic defects to inactive electron traps. The second interpretation “decrease of traps” may align with the successful incorporation of Sn as a donor and the high conductivity of Sn doped crystals revealed from Hall-effect measurements. This work also illustrates that the semi-insulating characteristics of Fe and Mg doped Ga2O3 are associated with the increase of the concentration of original traps in the crystal as well as the formation of new electron traps acting as deep acceptors. Recombination centers in all crystals are assumed to be associated with iron impurities.

Chemical manipulation of hydrogen induced high p-type and n-type conductivity in Ga2O3

“…The structure found here, in which the H + ion is bonded to one of the threefold coordinated oxygen ions, is similar to that described by Varley et al 9 Figure 2: Temperature dependent transport properties of the n-type and p-type H2 treated Ga2O3 samples. (a) sheet resistance, (b) sheet number, (c) sheet number logarithm plotted as a function of 1000/T D. THERMAL STIMULATED LUMINESCENCE SPECTROSCOPY (TSL): Thermal stimulated luminescence (TSL) spectroscopy [28][29][30][31][32] was performed on the samples to calculate the donor and acceptor ionization energies 30 . The measurements were performed using an in-house built spectrometer, 28,33 from -190 0 C to 25 0 C. The samples were first placed in a dark compartment and irradiated with UV light at -190°C for 30 min.…”

“…3a) is associated with the formation of shallow acceptors with ionization energy of 42 meV, calculated using the simplified model of TL developed by Randal and Williams. 28,31,34 The ionization energy of the donor, emerging after O2-annealing followed by H2-diffusion (green curve in Fig. 3a), was also calculated by the initial rise method from the peak at 111 K and found to be 20 meV.…”

Terahertz Emission Spectroscopy and Microscopy on Ultrawide Bandgap Semiconductor β-Ga2O3

“…We examine this question for the present case. The optical penetration depth at a photon energy of 4.8 eV is estimated to be approximately 125 nm based on the absorption measurement in [27]. Thus, Equation (1) is always valid.…”

Determination of Thermoluminescence Kinetic Parameters of La2O3 Doped with Dy3+ and Eu3+

“…Obtaining these temperatures with reasonable accuracy for an isolated peak is considered an effortless task. While it becomes puzzling if two glow peaks are overlapped and infeasible for the complex glow curves [50][51][52][53][54]. In most cases of the overlapped TL glow curves, one side of the peak interferes with other peaks.…”