Photoconductive gain modelling of GaN photodetectors

Abstract

A model to explain the behaviour of GaN photoconductive detectors is proposed, and it is based on the idea of a volume modulation rather than a carrier density modulation. Space charge regions inside the semiconductor produce a variation of the conductive volume when carriers are photogenerated. The strong non-exponential photocurrent decays result from carrier capture processes over the barriers associated with space charge regions. By means of computer simulation, this model explains quite well the behaviour of current GaN photoconductor devices and predicts their time response, temperature dependence and responsivity properties.

Ultrahigh-gain single SnO2 nanowire photodetectors made with ferromagnetic nickel electrodes

“…The spatial separation of electrons and holes reduces the electron-hole recombination rate; therefore, the electron lifetime is increased, and the photoresponse is enhanced. According to the simulation by Garrido et al, 33 the exponent k of the PC induced by the modulation of surface SCRs is between 0.5 and 0.9, which is in good agreement with our experimental measurements.…”

“…13 At intensities exceeding the critical value of the turning point, the value of the exponent k increases to a value of 0.6-0.8 as calculated from Figure 3b. Based on theoretical investigations, [30][31][32][33] the PC gain is now dominated by the modulation of surface space charge region (SCR). 30 The existence of oxygen vacancies on the surface of an SnO 2 NW causes the accumulation of free electrons on the NW surface.…”

“…The conductivity of NW is now dominated by the SCRs mechanism. 33 The current difference (dI) with and without magnetic field can be expressed as follows:…”

Characterization and modeling of a ZnO nanowire ultraviolet photodetector with graphene transparent contact

“…2 Therefore, the first term of the gain expression can account for gain values of the order of 30, which does not allow to explain the observed high gain. The second term in (3) reflects the modulation of the conducting cross-section due to the hole trapping at the lateral surface similar to the model described by Garrido et al 33 for 2D case. However, for the specific nanowire geometry with a very high surface to volume ratio, this term can be much stronger than in the 2D case.…”

“…Contrary to the planar case, 33 the dependence of the radius of conducting area in the dark R C0 on the surface potential V S cannot be obtained analytically. However, the numerical solution R C0 ðV S Þ of Eq.…”