Low‐Frequency Noise in AlGaN/GaN High Electron Mobility Transistors Irradiated by γ‐Ray Quanta

Abstract

Room temperature current-voltage and noise measurements have been made before and after gamma irradiation on AlGaN/GaN high electron mobility transistors (HEMTs) grown on sapphire. The saturation current due to radiation-induced defects shows a nonlinear dependence on radiation dose. The deviation of the device parameters does not exceed 20% at highest radiation dose 10 9 Rad and the devices with larger gate lengths demonstrate a higher radiation hardness to the 60 Co gamma rays. The noise spectra of devices after gamma irradiation follow the flicker noise (1/f g ) dependence with the exponent g close to one. The Hooge parameter estimated for the HEMTs after gamma irradiation dose does not show a gate-bias dependence and increases by approximately three to five times at radiation dose 2 Â 10 8 Rad. The analysis of noise spectra allowed to identify the major sources of noise generation in the investigated HEMT heterostructures.Introduction AlGaN/GaN heterostructures, in spite of a lattice mismatch between epilayers of different alloy composition as well as the substrate which may be a reason for structural defect formation, demonstrate unique noise properties [1]. Besides, due to a strong chemical bonding they are expected to be promising for broad applications in radiation environment [2]. Investigation of noise properties gives important information about defect structure in multiplayer semiconductor heterostructures, especially if additional traps are introduced under external irradiation. Up to now, noise properties in irradiated HEMTs have not been investigated. At the same time, such investigations are very important not only from fundamental point of view for obtaining substantial information on the physical properties of semiconductor materials and devices but also it gives limiting values of the device performance for application in space environment. It is essential that we introduce basic point defects by gamma irradiation in a controlling way. The changes in defect structure under gamma irradiation are usually accompanied by a charge carrier removal. Additionally, radiation induced transfer of the elemental components stimulated by ionisation processes takes place. In our previous work gated influence of gamma irradiation on basic operating parameters of the transistors, such as transconductance, channel conductance, and threshold voltage. In this paper, the effect of gamma irradiation on low-frequency noise spectra of AlGaN/GaN HEMTs with nanoscale gate length are reported. These measurements provide information about radiation hardness of the HEMTs and their high potential in satellite system applications.Experimental Details Transport and noise properties in AlGaN/GaN grown by organometallic vapour phase epitaxy (OMVPE) on sapphire substrates have been studied before and after gamma irradiation. The device layer structure was as follows: a 40 nm AlGaN (16% Al) nucleation layer grown on the substrate was followed by a 1.1 mm nominally undoped GaN buffer layer and a 23 nm n-AlGaN (33% Al) undoped bar...

Low-Noise Microwave Devices: AlGaN/GaN High Electron Mobility Transistors and Oscillators

“…If assembled with a high-quality whispering-gallery dielectric resonator (with Q 3x106) the phase noise value can be significantly decreased to -1 75dBc/Hz at 100 kHz. 5. Conclusion.…”

“…A state-of-the-art AlGaN/GaN high electron mobility transistor (TIEMT) can deliver: 1) a current cutoff frequency, fT, in excess of 181 GHz [2], 2) a minimum noise figure below 0.48 dB at 12 GHz [3] 3) a power density of 30 W/mm and a power-added efficiency of 49% in the X-band [4], and excellent radiation hardness [5]. The important characteristics of low noise amplifiers is the linearity of the microwave noise of GaN-based HEMTs [6], which will allow considerably lower noise levels than those in GaAs-based transistors.…”