PA-MBE Grown p-n (p-ZnO:(As+Sb)/<i>n</i>-GaN) and p-i-n (p-ZnO:As/HfO<sub>2</sub>/n-GaN) Heterojunctions as a Highly Selective UV Detectors

Abstract

Zinc oxide is a promising candidate for application in UV photodetectors due to the large direct band gap and the high absorption coefficient in the UV. The high quality p-n and p-i-n structures consist of single or dual acceptor doped ZnO:(As,Sb) films grown by MBE, thin HfO2 layer grown by ALD method and n-type GaN templates. The As and Sb concentrations is 1020 cm-3.The maximum forward-to-reverse current ratio IF/IR in the obtained p-n diodes is of about 105 at ±4 V and in the case of p-i-n diodes is of about 106, which are very good results for this type of heterojunctions. The UV photodetectors are highly selective. The maximum of the detection wavelength was found at about 365 nm (FWHM of the photocurrent peak is ~17 nm). In the case of p-i-n detectors, the maximum of detection was found at 376, 360, and 341 nm. Additionally, it is possible to control the detection range by the applied reverse voltage. The dark to light current ratio in both cases is ~104.