Quick measurement method of carbon-related defect concentration in n-type GaN by dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy

Dual-color-sub-bandgap-light-excited isothermal capacitance transient spectroscopy for quick measurement of carbon-related hole trap density in n-type GaN

“…In our previous study, we developed a method for the measurement of N T,H1 in n-type GaN layers that used subbandgap-light-excited isothermal capacitance transient spectroscopy (sub-E g -light ICTS). 10,11) In this method, a capacitance transient of a Schottky junction after sub-E g -light irradiation, of which the photon energy is below the bandgap (3.4 eV for GaN 12,13) ), is measured under constant reverse bias voltage (U R ), as shown in Fig. 1(a).…”

“…To obtain the true trap density, the hole occupancy ratio under each measurement condition should be determined. Therefore, in our previous report, 10,11) we focused on the filling period to estimate the hole occupancy ratio. Measurements were performed with various filling conditions, such as the measurement temperature, filling period (filling pulse width), and optical power.…”

“…( ˜) under various measurement conditions, f T was extracted from a calculation based on the rate equation and an accurate N T,H1 was obtained. 10,11) However, the previous methods are time-consuming due to the long time constant of hole thermal emission (t = e 1 , em t em t / e : em t hole thermal emission rate) of the H1 trap (e.g. time constant of hole emission t p ∼ 30 s at 300 K).…”

“…In this study, we focus on the measurement period, in which the hole is emitted from a hole trap to the valence band, and propose a quick method for the measurement of N T,H1 in n-type GaN using dual-color-sub-E g -light ICTS. 14) In this method, shorter wavelength light is irradiated as the filling pulse to cause the H1 trap to become a hole-occupied state. This is the same as our previously proposed methods.…”

“…In our previous study, it was shown that no dominant hole traps other than the H1 trap were detected, and N T,H1 was 2.3 × 10 15 cm −3 and the H1 trap was mainly associated with C N in the epilayer. 11) The capacitance transients of standard sub-E g -light ICTS and dual-color-sub-E g -light ICTS measurements are illustrated in Fig. 1(a).…”