HYDROGEN DOPED THIN FILM DIAMOND PHOTOTRANSISTOR/PHOTODIODE STRUCTURES FOR THE DETECTION OF UV RADIATION

摘要

The success of active electronic devices fabricated on CVD diamond has been hindered by the lack of shallow n or p-type dopants. However, UV photoconductors utilising the intrinsic form of the material have shown promising visible blind operational characteristics and there is clearly a market for simple robust devices of this nature. The recent emergence of near surface hydrogen doped CVD material, which exhibits useful room temperature electrical properties (p-type, high carrier concentration, low activation energy), has enabled the fabrication of diode and transistor structures with promising electrical characteristics. This paper reports the fabrication of two active optical detectors which utilise these structures; a metal-semiconductor-metal Schottky barrier device (MSM) and an optically controlled field effect transistor (OPFET). The performance of the two device structures is compared and their potential for use in deep UV visible blind detection is discussed. Device performance is strongly influenced by the contact properties of the ohmic and Schottky junctions which make up these structures. The circular transmission line method (c-TLM) has been used to examine, for the first time, the properties of different ohmic metallisations made to hydrogenated polycrystalline CVD diamond and the implications for improved device performance are discussed.