Review—Ionizing Radiation Damage Effects on GaN Devices

Abstract

Gallium Nitride based high electron mobility transistors (HEMTs) are attractive for use in high power and high frequency applications, with higher breakdown voltages and two dimensional electron gas (2DEG) density compared to their GaAs counterparts. Specific applications for nitride HEMTs include air, land and satellite based communications and phased array radar. Highly efficient GaNbased blue light emitting diodes (LEDs) employ AlGaN and InGaN alloys with different compositions integrated into heterojunctions and quantum wells. The realization of these blue LEDs has led to white light sources, in which a blue LED is used to excite a phosphor material; light is then emitted in the yellow spectral range, which, combined with the blue light, appears as white. Alternatively, multiple LEDs of red, green and blue can be used together. Both of these technologies are used in high-efficiency white electroluminescent light sources. These light sources are efficient and long-lived and are therefore replacing incandescent and fluorescent lamps for general lighting purposes. Since lighting represents 20-30% of electrical energy consumption, and because GaN white light LEDs require ten times less energy than ordinary light bulbs, the use of efficient blue LEDs leads to significant energy savings. GaN-based devices are more radiation hard than their Si and GaAs counterparts due to the high bond strength in III-nitride materials. The response of GaN to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. The latter can act as sinks for created defects and parameters such as the carrier removal rate due to trapping of carriers into radiation-induced defects depends on the crystal growth method used to grow the GaN layers. The growth method has a clear effect on radiation response beyond the carrier type and radiation source. We review data on the radiation resistance of AlGaN/GaN and InAlN/GaN HEMTs and GaN-based LEDs to different types of ionizing radiation, and discuss ion stopping mechanisms. The primary energy levels introduced by different forms of radiation, carrier removal rates and role of existing defects in GaN are discussed. The carrier removal rates are a function of initial carrier concentration and dose but not of dose rate or hydrogen concentration in the nitride material grown by Metal Organic Chemical Vapor Deposition. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance. State-of-art simulators now provide accurate predictions for the observed changes in radiation-damaged HEMT performance. Neutron irradiation creates more extended damage regions and at high doses leads to Fermi level pinning while 60 Co γ-ray irradiation leads to much smaller changes in HEMT drain ...

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

“…However, the rate of recovery observed in this work is rather surprising since the recovery time of several weeks at room temperature is usually reported in the literature. 39 Self-annealing of irradiation induced defects at room temperature is reported over a month period in the case of the InGaAs/GaAs quantum well by Dhaka et al 40 Similarly, a self-recovery of neutron irradiated AlGaN/GaN high electron mobility transistor (HEMT) devices is reported by Kim et al 41 where the electrical response of the device completely recovered within 3 weeks of irradiation. The only difference is that our devices recover within a day which might be governed by the extent of damage caused by a different type of irradiation in our experiments.…”

Design and radiation tests on a LED based emergency evacuation directional lighting

“…However some recent reports do exist for the same materials as used for the Cree XP-E2 LEDs. Blue LEDs made of InGaN are reported to decrease its luminance by about 18% and 47% for 340 keV proton doses of respectively 1x10 12 and 5 x 10 12 proton/cm 2 [4]. The InGaN is the same technology used for the green Cree XP-E2 LED that during the CHARM test shows a decrease of about 30% for a dose of 870 Gy and 2.3 x 10 12 HEH/cm 2 .…”

Optical Investigation of Proton‐Irradiated Metal Organic Chemical Vapor Deposition AlGaN/GaN High‐Electron‐Mobility Transistor Structures

“…The technology is particularly appealing for microwave power amplifiers and direct current (DC)/DC converters in space‐based applications due to the high tolerance to the space radiation environment. It has previously been shown that the DC I–V characteristics exhibit high‐tolerance displacement damage induced by proton irradiation and devices exhibit reduced leakage current and increased breakdown voltage but at the expense of substantially increased dynamic ON resistance . However, there has not been a thorough spectroscopic evaluation of such device structures to identify the nature of the traps induced by displacement damage.…”

“…It has previously been shown that the DC I-V characteristics exhibit high-tolerance displacement damage induced by proton irradiation and devices exhibit reduced leakage current and increased breakdown voltage but at the expense of substantially increased dynamic ON resistance. [1][2][3][4][5] However, there has not been a thorough spectroscopic evaluation of such device structures to identify the nature of the traps induced by displacement damage.…”