Effect of 60Co γ-irradiation on the nature of electronic transport in heavily doped n-type GaN based Schottky photodetectors

Abstract

GaN Schottky photodetectors are fabricated on heavily doped n-type GaN epitaxial layers grown by the hydride vapour phase epitaxy technique. The effect of 60Co γ-radiation on the electronic transport in GaN epilayers and Schottky detectors is studied. In contrast to earlier observations, a steady rise in the carrier concentration with increasing irradiation dose is clearly seen. By considering a two layer model, the contribution of interfacial dislocations in carrier transport is isolated from that of the bulk layer for both the pristine and irradiated samples. The bulk carrier concentration is fitted by using the charge balance equation which indicates that no new electrically active defects are generated by γ-radiation even at 500 kGy dose. The irradiation induced rise in the bulk carrier concentration is attributed to the activation of native Si impurities that are already present in an electrically inert form in the pristine sample. Further, the rise in interfacial contribution in the carrier concentration is governed by the enhanced rate of formation of nitrogen vacancies by irradiation, which leads to a larger diffusion of oxygen impurities. A large value of the characteristic tunnelling energy for both the pristine and irradiated Au/Ni/GaN Schottky devices confirms that the dislocation-assisted tunnelling dominates the low temperature current transport even after irradiation. The advantage of higher displacement energy and larger bandgap of GaN as compared to GaAs is evident from the change in leakage current after irradiation. Further, a fast recovery of the photoresponse of GaN photodetectors after irradiation signifies their compatibility to operate in high radiation zones. The results presented here are found to be crucial in understanding the interaction of 60Co γ-irradiation with n+-GaN epilayers.

The effect of low dose γ-irradiation on the optoelectric properties of n-GaN based MSM structure

“…The dark current increased to 61.65 μA in +2 volt in first step. An initial current enhancement at the first step followed by a gradual decrease upon gamma dose increasing in the next shorter steps, as shown in the inset picture for 1.4 V. This observation is not similar to the earlier observations for the higher doses 1,[18][19][20][21] . Thereafter, the sample left for 24 hours and then repeated the I-V test.…”

“…Gallium nitride (GaN) and its related alloys such as AlxGa1-xN and InxGa1-xN are widely used in the ultraviolet (UV) and visible spectrum regions, especially as the active region of photodetectors (PD) 1 . III-nitride-based PDs are particularly commonly used in harsh environments such as space applications 2,3 Meanwhile, the wide bandgap (3.4 eV 2 ), high breakdown voltage 4 , thermal and chemical stability, and irradiation resistance introduce GaN as a suitable candidate to use in harsh and irradiated environments.…”

“…5,6 Exposure of the GaN layers with electromagnetic irradiation and/or high-energy particles has been shown to lead to the vacancy generation and defects in the crystal structure such as Ga and/or N atoms displacements from their respective lattice sites 7 . This phenomenon generates new energy levels in the bandgap, which act as scattering centers such as donor, acceptor, or recombination centers 1,8 . Therefore, it is crucial to study the irradiation effects on semiconductor devices to understand the behavior of optoelectric devices in irradiation environments and fulfill the materials and design requirements consequently.…”

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“…The ideality factor and the Schottky barrier height are main parameters for gate-ch of InP-based HEMTs. According to the thermionic-emission model, the ideality factor and the Schottky barrier height can be obtained from the slope and intercept of Ln I-V plot, the equations can be written as: [23][24][25] ,…”

Role of ZrO2 Passivation Layer Thickness in the Fabrication of High‐Responsivity GaN Ultraviolet Photodetectors

“…In case of III‐nitrides, threading dislocations are considered as an alternate conduction path, which often lead to high leakage current in Schottky diodes . The presence of a large density of dislocations ( N dis ) at the GaN/sapphire interface in similar HVPE grown 5 μm thick GaN samples including their adverse effect on the optoelectronic properties of devices made out of them is already reported by us . Here, the value of N dis is estimated to be 6 × 10 10 cm −2 at the GaN/sapphire interface, which reduces by an order of magnitude while moving away from the interface …”