Ultraviolet-sensitive, visible-blind GaN photodiodes fabricated by molecular beam epitaxy

Abstract

GaN p–i–n photovoltaic diode arrays were fabricated from epitaxial films deposited on sapphire by molecular beam epitaxy. Peak UV responsivity was 0.11 A/W at 360 nm, corresponding to 48% internal quantum efficiency. Visible rejection over 400–800 nm was 3–4 orders of magnitude. Typical pulsed time response was measured at 8.2 μs. Spectral response modeling was performed to analyze the photocurrent contributions from photogenerated carrier drift in the depletion region and from minority carrier diffusion in the p and n layers. With the model, a maximum internal quantum efficiency of 55% at 360 nm was calculated for the photovoltaic diode structure.

Fabrication and Characterization of GaN/AlGaN Ultraviolet-Band Heterojunction Photodiodes

“…In calculating the responsivity of the device we take into account contributions to the photocurrent that originate from photogenerated holes in the n-Al 0.1 Ga 0.9 N layer that diffuse towards the depletion region, from the drift of photogenerated carriers in the depletion regions of the Al 0.1 Ga 0.9 N and the GaN, and from the diffusion of electrons in the p-GaN layer diffusing towards the depletion region [4]. The device is assumed to be illuminated through the n-Al 0.1 Ga 0.9 N layer , with reflections at the air/sapphire and the sapphire/detector interfaces taken into account in the model.…”

“…Although photoconductive detectors have the desirable property of internal gain, they suffer from well known drawbacks which include high dark currents, DC drift, slow response time, and occasionally spurious photoresponse at long wavelengths. Recently, relatively fast photovoltaic UV detection using GaN p-n diodes or Schottky diodes has been demonstrated [4] [5] [6]. A key advantage of III-nitride detectors over competing devices based on semiconductors with smaller bandgaps (for example UV-enhanced Si photodetectors) is the long wavelength response cut-off which is directly related to the bandgap of the material in the active region and thus does not require external filters.…”

Uniformity and Performance Characterization of GaN p-i-n Photodetectors Fabricated from 3-Inch Epitaxy

“…Details of the growth process have been previously reported [5][6]. The detector epitaxial layers consisted of a 5·10 18 cm -3 n-GaN layer followed by a 5000 Å intrinsic region with unintentional n-type doping in the 10 15 cm -3 decade.…”

Electric force microscopy of induced charges and surface potentials in GaN modified by light and strain

“…5 It has been recently demonstrated that the large intrinsic piezoelectric coefficients of GaN and AlN are responsible for an anomalously large concentration of two-dimensional electron gas at the AlGaN/GaN interface in GaN/AlGaN heterojunction field effect transistors ͑HFET͒. 6,7 Other possibilities exist for the enhancement of electric properties of contacts to nitrides by piezoelectric engineering as recently demonstrated in the case of Schottky contacts.…”