Buffer Traps in Fe-Doped AlGaN/GaN HEMTs: Investigation of the Physical Properties Based on Pulsed and Transient Measurements

Abstract

This paper presents an extensive investigation of the properties of the trap with activation energy equal to 0.6 eV, which has been demonstrated to be responsible for current collapse (CC) in AlGaN/GaN HEMTs. The study was carried out on AlGaN/GaN HEMTs with increasing concentration of iron doping in the buffer. Based on pulsed characterization and drain current transient measurements, we demonstrate that for the samples under investigation: 1) increasing concentrations of Fe-doping in the buffer may induce a strong CC, which is related to the existence of a trap level located 0.63 eV below the conduction band energy and 2) this trap is physically located in the buffer layer, and is not related to the iron atoms but—more likely—to an intrinsic defect whose concentration depends on buffer doping. Moreover, we demonstrate that this level can be filled both under OFF-state conditions (by gate-leakage current) and under ON-state operation (when hot electrons can be injected to the buffer): for these reasons, it can significantly affect the switching properties of AlGaN/GaN HEMTs

Identification of an RF degradation mechanism in GaN based HEMTs triggered by midgap traps

“…From the peak height, the sheet concentration of E C -0.57 eV trap detected after stressing was in the order of 1.5 × 10 11 cm −2 . These observations suggest that there is a clear relationship between the reverse gate leakage and the E C -0.57 eV trap in agreement with recent reports in literature that propose the high offstate gate leakage may be a filling mechanism (and necessary condition) that enables detection of the E C -0.57 eV trap [12]. Apart from the E C -0.57 eV trap, the GaN devices also showed presence of an E C -0.72 eV electron trap at concentrations of 8.8 × 10 12 cm −2 before stressing that slightly increased to 9.2 × 10 12 cm − 2 , which causes a small increase of drain resistance from 0.10 to 0.13 Ω-mm.…”

Hot-Electron Degradation of AlGaN/GaN High-Electron Mobility Transistors During RF Operation: Correlation With GaN Buffer Design

“…and 10 17 cm −3 C-doped buffer devices is caused by an increase of the concentration of the traps with activation energy E A = 0.79 eV and capture cross-section σ c = 6 × 10 −13 cm 2 (labelled E3) and E A = 0.84 eV, σ c = 4 × 10 −14 cm 2 (labelled E4) [12], [13]. On the other hand, though devices with 10 18 cm −3 Fe-and 10 18 cm −3 C co-doping feature higher initial current dispersion (mainly caused by the trap E2, with E A = 0.56 eV and σ c = 5 × 10 −15 cm 2 [14]), they experience negligible decrease of the dynamic transconductance and negligible increase of trap density after RF operations. The Arrhenius plot with the signatures of the detected deep-levels is reported in Figure 7.…”

Trapping Analysis of AlGaN/GaN Schottky Diodes via Current Transient Spectroscopy

“…Measurement was performed in a temperature range between 25 and 150˝C using a heated plate and an ATT Systems A150 temperature controller. (e.g., [14,17,20,21]) and between 0.71 and 0.82 eV (e.g., [1,9,19,[22][23][24]) were the most commonly reported. Unfortunately, their origin remains ambiguous.…”