Photoresponse and Defect Levels of AlGaN/GaN Heterobipolar Phototransistor Grown on Low-Temperature AlN Interlayer

Abstract

We report on a visible-blind AlGaN/GaN heterobipolar phototransistor with low threading dislocation density, fabricated by organometallic vapor phase epitaxy using the low-temperature interlayer technique. The dark current at room temperature was as low as 34.6 pA/mm² at 3 V and the responsivity was 160 A/W under 0.78 nW/cm² illumination. The high-temperature device performance up to 200°C was marked by the exponential evolution of the dark current under the influence of a deep defect near 459 meV. Also, photoinduced transient spectroscopy between 50°C and 175°C yielded evidence of defects at about 93 meV, 137 meV and 205 meV energies, which caused a long-lasting photocurrent after weak-intensity illumination.