InGaN/GaN Multiquantum-Well Metal-Semiconductor-Metal Photodetectors With Beta-${\rm Ga}_{2}{\rm O}_{3}$ Cap Layers

Abstract

InGaN/GaN multiquantum-well (MQW) metal-semiconductor-metal photodetectors with a beta-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> cap layer formed by the furnace oxidation of a GaN epitaxial layer are fabricated and characterized. The beta-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> cap layer is found to suppress the reverse leakage current by at least about two orders of magnitude with a 5-V applied bias because it creates a thicker and higher potential barrier. The reverse leakage current can be further reduced and a 90-fold larger ultraviolet-to-visible rejection ratio can be achieved by using InGaN/GaN MQW layers, which confine the electron-hole pairs generated by lower-energy photons. In addition, the noise level is reduced and detectivity is increased. With a 5-V applied bias, the noise-equivalent power and normalized detectivity are 8.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-13</sup> W and 7.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively.