title: A microfabricated sun sensor using GaN-on-sapphire ultraviolet photodetector arrays.
abstract: A miniature sensor for detecting the orientation of incident ultraviolet light was microfabricated using gallium nitride (GaN)-on-sapphire substrates and semi-transparent interdigitated gold electrodes for sun sensing applications. The individual metal-semiconductor-metal photodetector elements were shown to have a stable and repeatable response with a high sensitivity (photocurrent-to-dark current ratio (PDCR) = 2.4 at -1 V bias) and a high responsivity (3200 A/W at -1 V bias) under ultraviolet (365 nm) illumination. The 3 × 3 GaN-on-sapphire ultraviolet photodetector array was integrated with a gold aperture to realize a miniature sun sensor (1.35 mm × 1.35 mm) capable of determining incident light angles with a ±45° field of view. Using a simple comparative figure of merit algorithm, measurement of incident light angles of 0° and 45° was quantitatively and qualitatively (visually) demonstrated by the sun sensor, supporting the use of GaN-based sun sensors for orientation, navigation, and tracking of the sun within the harsh environment of space.
authors: Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, USA.
authors: Ruth A
authors: RA
authors: Miller
authors: Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, USA.
authors: Hongyun
authors: H
authors: So
authors: Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, USA.
authors: Heather C
authors: HC
authors: Chiamori
authors: Mechanical Engineering, Stanford University, Stanford, California 94305, USA.
authors: Ateeq J
authors: AJ
authors: Suria
authors: Mechanical Engineering, Stanford University, Stanford, California 94305, USA.
authors: Caitlin A
authors: CA
authors: Chapin
authors: Department of Aeronautics and Astronautics, Stanford University, Stanford, California 94305, USA.
authors: Debbie G
authors: DG
authors: Senesky