ZnSe-BASED SOLAR-BLIND ULTRAVIOLET PHOTODETECTORS WITH DIFFERENT SCHOTTKY CONTACT METALS

Vadim P. SIRKELI, Natalia D. NEDEOGLO, Dmitrii D. NEDEOGLO, Oktay YILMAZOGLU*, Ahid S. HAJO*, Sascha PREU*, Franko KÜPPERS*, Hans L. HARTNAGEL* Moldova State University *Technische Universität Darmstadt, Darmstadt, Germany

Abstract

We report on the selection of contact metallisations for ZnSe-based metal-semiconductor-metal ultraviolet photode- tectors. Our evaluation is based on Ni/Au, Cr/Au, and hybrid Ag-nanowire contacts. Low values of dark current of 0.32 nA, 0.82 nA and 1.64 nA at bias voltage of 15 V were achieved for photodetectors with Ag-NW, Ni/Au and Cr/Au interdigital contacts, respectively. The best performance of our ZnSe-based ultraviolet photodetectors is observed for Ni/Au interdigital contacts. This is due to the higher Schottky barrier height, which is equal to ~ 1.49 eV for Ni/Au contacts in comparison with ~ 1.26 eV for Cr/Au contacts. A very high responsivity of 5.40 AW -1 at bias voltage of 15 V for light with a wave- length of 325 nm is obtained for devices with Ni/Au interdigital contacts. Moreover, the maximum of photocurrent on/off ratio of 20342 and minimum of NEP of ~ 3 × 10 -15 W Hz -1/2 at bias voltage of 15 V was achieved for this type of device. Keywords: zinc selenide, metal-semiconductor-metal structures, Schottky diodes, ultraviolet photodetectors, impact ionization.