Abstract: A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

Abstract: The apparatus 11 according to the present invention effectively eliminates losses to reflection and/or secondary emission of the charged particle beam 13 being measured. It comprises a sense cup (17) with an interior chamber and an entry opening (25) through which the charged particle beam (13) enters. A sense cone (19) forms the rear wall of the interior chamber with the cone apex adjacent the entry opening (25). An outer case (21) surrounds the sense cup (17) and is electrically insulated therefrom. Charged particles entering the interior chamber are trapped and are absorbed by the sense cup and cone and travel through a current measuring device (15) to ground.