Deep trap spectra of Sn-doped α-Ga2O3 grown by halide vapor phase epitaxy on sapphire

Abstract

Epitaxial layers of α-Ga2O3 with different Sn doping levels were grown by halide vapor phase epitaxy on sapphire. The films had shallow donor concentrations ranging from 1017 to 4.8 × 1019 cm−3. Deep level transient spectroscopy of the lowest doped samples revealed dominant A traps with level Ec − 0.6 eV and B traps near Ec − 1.1 eV. With increasing shallow donor concentration, the density of the A traps increased, and new traps C (Ec − 0.85 eV) and D (Ec − 0.23 eV) emerged. Photocapacitance spectra showed the presence of deep traps with optical ionization energy of ∼2 and 2.7 eV and prominent persistent photocapacitance at low temperature, surviving heating to temperatures above room temperature. The diffusion length of nonequilibrium charge carriers was 0.15 µm, and microcathodoluminescence spectra showed peaks in the range 339–540 nm, but no band-edge emission.

Analysis of Deep Traps in Mist Chemical Vapor Deposition‐Grown n‐Type α‐Ga2O3 by Photocapacitance Method

“…The rectification ratio of forward and reverse current is %10 5 , so when applying reverse bias voltage to the sample, almost all bias voltage is applied to the depletion region of the Schottky contact (see Experimental Section). This result showed that the donor concentration in this SBD was well suppressed compared with that in the study by Polyakov et al, [36] suggesting higher purity and better Schottky characteristic of our sample.…”

“…In the studies on α-Ga 2 O 3 previously reported, deep traps located at E c À1 eV, E v þ1.4 eV [35,37] and located at E c À(%2 eV), E c À2.7 eV are confirmed. [36] Here, E v corresponds to the valence band maximum. The PHCAP spectra obtained in the study by Polyakov et al [36] seem to resemble that obtained in this study (Figure 5a).…”

“…[34] In this study, we aim at detecting traps near the midgap because such traps have reported to give great influences on properties of β-Ga 2 O 3 . [12,[14][15][16]18,20,21,23,26] For α-Ga 2 O 3 , trap levels are evidenced relatively near the conduction band minimum by means of the temperature dependence of the dark current [35] and DLTS [36,37] as well as near the midgap and in the lower half of the bandgap by PICTS, [35] PHCAP, [36] and ODLTS. [37] The PHCAP and DLOS are suitable for detecting deep traps because the bandgap is so large that deep traps are ionized by conventional visible light.…”

“…Therefore, it is necessary to conduct both the PHCAP and DLOS for an α-Ga 2 O 2 Schottky barrier diode (SBD) to elucidate the accurate nature of deep traps of α-Ga 2 O 3 . In addition, intervals of photon energy of the irradiated monochromatic light in the study by Polyakov et al [36] are too broad to identify the actual trap levels accurately, so it is also necessary to conduct these measurements at smaller intervals of photon energy. In this article, we report the results of PHCAP and DLOS characterization of α-Ga 2 O 3 grown by mist chemical vapor deposition (CVD).…”

Влияние влажности окружающей среды на электрическую проводимость полиморфных Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=--структур

“…Достигнут значительный прогресс в выращивании эпитаксиальных пленок [1][2][3][4][5][6][7][8][9]. Корундообразная α-фаза обладает среди всех политипов оксида галлия наибольшей шириной запрещенной зоны E g , не менее 5.3 эВ, и при легировании Sn или Si имеет высокую донорную проводимость [3,8,[10][11][12][13][14][15]. В то же время ε-фаза с E g , близкой к 4.9 эВ [1,2,16], является второй после β-Ga 2 O 3 по температурной стабильности.…”