Hole traps and persistent photocapacitance in proton irradiated β-Ga2O3 films doped with Si

Abstract

Hole traps in hydride vapor phase epitaxy β-Ga2O3 films were studied by deep level transient spectroscopy with electrical and optical excitation (DLTS and ODLTS) and by photocapacitance and temperature dependence measurements. Irradiation with 20 MeV protons creates deep electron and hole traps, a strong increase in photocapacitance, and prominent persistent photocapacitance that partly persists above room temperature. Three hole-trap-like signals H1 [self-trapped holes (STH)], H2 [electron capture barrier (ECB)], and H3, with activation energies 0.2 eV, 0.4 eV, 1.3 eV, respectively, were detected in ODLTS. The H1 (STH) feature is suggested to correspond to the transition of polaronic states of STH to mobile holes in the valence band. The broad H2 (ECB) feature is due to overcoming of the ECB of the centers responsible for persistent photocapacitance for temperatures below 250 K. The H3 peak is produced by detrapping of holes from Ev + 1.3 eV hole traps believed to be related to gallium vacancy acceptors. One more deep acceptor with optical ionization threshold near 2.3 eV is likely responsible for high temperature persistent photocapacitance surviving up to temperatures higher than 400 K. The latter traps show a significant barrier for capture of electrons.

Hydrogen plasma treatment of β -Ga2O3: Changes in electrical properties and deep trap spectra

“…After annealing at 450 C, the diffusion length was 70 nm, and after 550 C, it was 80 nm. The donor concentration and the E2 Ã and E3 trap concentrations in the reference sample were an order of magnitude higher than in HVPE films studied by us previously, 20,24,25 which correlates with the lower L d in the reference sample compared to previously reported for HVPE b-Ga 2 O 3 [L d $ 450 nm (Refs. 20, 24, and 25)].…”

“…DLTS spectra showed two major peaks belonging to electron traps with levels near E c -0.8 eV and E c -1.05 eV, with signatures close to those of the electron traps E2 Ã and E3. [23][24][25] Figure 2 shows the spectra obtained with a reverse bias of À5 V pulsed to 0 V for 3 s for DLTS time windows t 1 /t 2 ¼ 1.75 s/17.5 s. The y-axis in the figure represents the DLTS signal DC/C multiplied by 2 N d and divided by the DLTS spectrometer function F ¼ exp(Àt 2 /s) À exp(Àt 1 /s), with s ¼ (t 2 À t 1 )/ln (t 2 /t 1 ). 18 The convention is that positive peaks correspond to electron traps (capacitance increases during the capacitance transient 18 ).…”

Electrical properties of bulk semi-insulating β-Ga2O3 (Fe)

“…Their concentration is higher than in undoped bulk crystals, $10 16 cm À3 , which could be related to defect formation upon Fe doping. 28 In conclusion, heavy Fe doping used to obtain semiinsulating bulk b-Ga 2 O 3 does not induce the formation of high densities of deep electron and hole traps other than the center near E c À 0.8 eV ascribed to Fe. With the high Fe concentrations used to compensate shallow donors in bulk undoped EFG crystals, the density of the empty Fe states available for trapping in FETs on these buffers will always produce current collapse in the pulsed operation mode.…”

An Artificial Optoelectronic Synapse Based on a Photoelectric Memcapacitor

“…Besides, the photo electric memcapacitors require only small AC voltages for the capacitance detection. [31][32][33][34][35] With this consideration, we design a planar Au/ La 1.875 Sr 0.125 NiO 4 (LSNO)/Au MSM structure (Figure 1b) for the demonstration of photoelectric memcapacitors. In addition, the photo electric memcapacitors can be made with a planar metal/semiconductor/metal (MSM) structure, which has many advantages, including simple device structure, large photosensing area, ultralow leakage current, and high sensitivity.…”