In recent years, AlGaN semiconductor alloys, with a direct bandgap tunable between 3.4eV and 6.2eV, become the most
suitable material for fabricating UV detectors. In this paper, a backside-illuminated visible-blind UV detector based on a
GaN/AlGaN p-i-n heterostructure has been successfully fabricated and tested. The p-i-n photodiode structure consists of
a 0.7um n-type Al0.33Ga0.67N:Si layer grown by metal-organic chemical vapor deposition (MOCVD) onto a low
temperature AlN buffer layer on a polished sapphire substrate. On the top of this layer there is a 0.18um undoped GaN
active layer and a 0.15um p-type GaN:Mg top layer. Square mesas of area A=1.70×10-3cm2 were obtained by inductively coupled plasma etching using BCl3, Ar and Cl2. Standard photolithographic and metallization procedures were also employed to fabricate the devices. The visible blind photodiode exhibits a narrow UV spectral responsibility band
peaked at 360nm, with maximum responsibility R=0.21A/W, corresponding to an internal quantum efficiency of 82%.
R0A values up to 2.64×108Ω•cm2 were obtained, corresponding to D*=2.65×1013 cmHz1/2W-1 at 360nm. The leakage
current at zero bias is 5.20×10-13A. We also examined GaN/AlGaN epitaxial layers by high resolution X-ray diffraction (HRXRD). The rocking curve indicates the multiple layers including p-type layer are in good state, which indicates that
the crystalline quality of films is the key of device performances.