High-responsivity photoconductive ultraviolet sensors based on insulating single-crystal GaN epilayers

Abstract

We report on the fabrication and characterization of photoconductive ultraviolet detectors based on insulating single-crystal GaN. The active layer (GaN) was deposited over basal-plane sapphire substrates using a unique switched atomic-layer-epitaxy process. The sensors were measured to have a responsivity of 2000 A/W at a wavelength of 365 nm under a 5-V bias. The responsivity remained nearly constant for wavelengths from 200 to 365 nm and dropped by three orders of magnitude within 10 nm of the band edge (by 375 nm). We estimate our sensors to have a gain of 6×103 (for wavelength 365 nm) and a bandwidth in excess of 2 kHz. The photosignal exhibited a linear behavior over five orders of incident optical power, thereby implying a very large dynamic range for these GaN-based ultraviolet sensors.

Characterization and Modeling of Photoconductive GaN Ultraviolet Detectors

“…A frequency dependence of the responsivity has also been detected [7] [11]. Reported data also indicate a very non-linear behavior, with a photoconductive gain decreasing with the optical power [5] [7]. In this work we present a study of the physical mechanism of photoconductive gain in GaN epitaxial layers, and the computer implementation of a novel model that matches our experimental results quite precisely.…”

“…Some of the characteristics of GaN photoconductors have been reported. There is a general agreement on the presence of an abnormally high responsivity [5] [6] [9] and persistent photoconductivity [7] [10] [11], which have been tentatively attributed either to deep levels [9] or to Mg-doping related centers [8]. A frequency dependence of the responsivity has also been detected [7] [11].…”

“…Photocoductive GaN detectors have early attracted a significant interest [5] [6] [7] [8] [9]. For their simplicity, they are candidates as low cost UV detectors in consumer and environmental applications.…”

Electrical Characterization of Traps in AlGaN/GaN FAT-HEMT’s on Silicon Substrate by C-V and DLTS Measurements

“…A new market thus emerges in the field of telecommunications with High Electronic Mobility Transistors (HEMT's) which can support power densities 10 times higher than those accessible with the silicon and gallium arsenide technologies as reported by Dumka et al [6], as well as cut-off frequencies higher than 100 GHz were reported in a previous paper [7]. These HEMT's structures are essential to meet the increasing needs for the communication systems requiring high power and frequency applications [8][9][10] (radars, stations of bases, connection satellite). Due to their strong thermal conductivity and good performance stability in a hostile environment, GaN-based HEMT devices are excellent candidates especially in high power/frequencies domain.…”

Fabrication and Characterization of GaN/Polymer Composite p-n Junction with PEDOT Nanoparticle Interface Layer

“…These electronic and optoelectronic devices included visible light-emitting diodes (LED) [1], metal semiconductor field effects transistors (MESFET) [2], high electron mobility transistors (HEMT) [3], UV photoconductive detectors [4], and UV photovoltaic detectors [5]. The fabrication of the devices requires performing a controlled and reproducible n-and p-type doping.…”