Analysis and modeling of AlxGa1−xN-based Schottky barrier photodiodes

Abstract

Schottky barrier photovoltaic detectors have been fabricated on n-AlxGa1−xN(0⩽x⩽0.35) and p-GaN epitaxial layers grown on sapphire. Their characteristics have been analyzed and modeled, in order to determine the physical mechanisms that limit their performance. The influence of material properties on device parameters is discussed. Our analysis considers front and back illumination and distinguishes between devices fabricated on ideal high-quality material and state-of-the-art heteroepitaxial AlxGa1−xN. In the former case, low doping levels are advisable to achieve high responsivity and a sharp spectral cutoff. The epitaxial layer should be thin (<0.5 μm) to optimize the ultraviolet/visible contrast. In present devices fabricated on heteroepitaxial AlxGa1−xN, the responsivity is limited by the diffusion length. In this case, thick AlxGa1−xN layers are advisable, because the reduction in the dislocation density results in lower leakage currents, larger diffusion length, and higher responsivity. In order to improve bandwidth and responsivity, and to achieve good ohmic contacts, a moderate n-type doping level (∼1018 cm−3) is recommended.

Cathodoluminescence Studies of Electron Injection Effects in Wide-Band-Gap Semiconductors

“…It can be seen from the left inset of Fig. 14 that the inverse square root of intensity increases linearly for all temperatures. The temperature dependence of rate, R, can be used to determine the activation energy of the irradiation-induced processes according to equation (15). On the other hand, our earlier studies of the temperature-induced CL intensity decay (Sec.…”

“…The relationship between minority carrier diffusion length and responsivity of Schottky photodiodes has been examined in great detail in Ref. [15]. Schottky photodiodes are among the simplest photovoltaic devices, where the non-equilibrium minority carriers, generated in the bulk of the semiconductor due to light absorption, are collected by the built-in field of the Schottky barrier deposited on the surface of the semiconductor.…”

“…Since only the carriers within a few diffusion lengths of the space-charge region contribute to photocurrent, the responsivity at below-bandgap energies is limited by the diffusion length (unless the diffusion length exceeds the thickness of the absorber layer, in which case the latter is the limiting factor) [15].…”

Thermal admittance spectroscopy of Mg-doped GaN Schottky diodes

“…[2][3][4][15][16][17][18][19] One interest of electrical studies is to confirm the presence of the Mg dopants and their electrical activity, and to deduce microscopic parameters such as ionization energies, capture cross sections, spatial concentration profiles, etc. Another interest is to contribute to the basic understanding of the conduction mechanism in these structures as the performances of the various electronic and optoelectronic devices depend on the efficiency of the current injection and of the carrier generation or carrier recombination.…”

Solar-blind AlGaN-based Schottky photodiodes with low noise and high detectivity

“…2 Moreover, its intrinsic solar blindness ͑for x у0.38) and the ability of operation under harsh conditions ͑high-temperature and high power levels͒ due to its wide band gap makes Al x Ga 1Ϫx N-based photodetectors attractive for high-performance solar-blind detection applications. Several research groups have demonstrated successful solarblind operation with Al x Ga 1Ϫx N photodetectors using photoconductive, 3,4 p -i -n, [5][6][7][8][9][10][11][12][13][14] metal-semiconductormetal ͑MSM͒, 15,16 and Schottky [17][18][19][20] detector structures. Cutoff wavelengths ( c ) as short as ϳ225 nm, an ultraviolet/ visible rejection over 5 orders of magnitude along with responsivities as high as 0.12 A/W at 232 nm were reported using a Al 0.7 Ga 0.3 N p -i -n detector structure.…”