High-Temperature Operation of Al0.5Ga0.5N/AlN Solar-Blind Phototransistor With Built-In Polarization Photogate

This letter reports the high-temperature operation of n-Al0.5Ga0.5N/AlN solar-blind field-effect phototransistor with built-in polarization photogate. A very low dark current below 6 pA was demonstrated at 1 V drain bias in the temperature range of 20 °C to 300 °C. The dark current increases with bias and temperature, while the photocurrent exhibits different trends with temperature at high and low drain bias. At 300 °C, the resulting photo-to-dark current ratio is
$8.3\times 10^{{7}}$
at 1 V, and can still reach
$2.5\times 10^{{2}}$
at 10 V. In contrast, the responsivity is
$2.9\times 10^{{3}}$
A/W at 1 V and 260 nm, and increases to a record high value of
$4.5\times 10^{{4}}$
A/W at 10 V. The common persistent photoconductivity seen in field-effect phototransistors consistently improves with increasing temperature, attributed to carrier detrapping from deep levels.