Ultraviolet Photo-detective Characteristics of ...

A room-temperature anisotropic photo-electro-chemical etching process for n-type GaN films using a potassium hydroxide (KOH, pH=1.09~1.39) and phosphoric acid (H3PO4, pH=12.60~12.90) in the stirrer solution and Deuterium lamp illumination is described. The process provides anisotropic etch profiles and high etch rates >240 nm/ min at moderate light intensities ~17.3 mW/cm2 @237 nm in the H3PO4 (pH=1.09) solution. The etch rate and photocurrent are characterized as a concentration of the stirred solutions. In this work, two types of metal-oxide-semiconductor (MOS) structures were fabricated. One is the semiconductor layer with as-grown n-GaN (Sample B), and the other is the n-GaN surface with photo-electro-chemical etching (Sample A). The oxide layer for both these devices were fabricated using silicon dioxide insulator grown by a low-temperature (30-40℃) and reliable method of liquid phase deposition (LPD). For an incident light wavelength of 366 nm with an intensity of 4.15 mW/cm2 and a 6 V reverse bias, it was found that the photo to dark current ratio was around 31 and 26 for sample A and B, respectively. The photo to dark current ratio of sample A increases 19.2% compares with sample B.