Abstract
The electron trapping in AlGaN/GaN high-electron mobility transistors (HEMTs) with iron (Fe)-doped buffer is investigated through Drain Current Transient (DCT) measurements and TCAD physics-based 2D device simulations. The DCT characterization reveals two prominent deep-level electron traps E1 (∼0.5 eV) and E2 (∼0.6 eV) in the AlGaN/GaN HEMT. The measured DCT spectrum is analyzed at different trap-filling pulse durations (10 µs–100 ms) to obtain the information of trapping kinetics. As the first step in the simulation, the TCAD physical model parameters are calibrated by matching the simulated DC characteristics with the experimental data. It is shown that the TCAD model incorporating the acceptor-type trap at EC – 0.5 eV in the GaN buffer quantitatively reproduces the measured DCT spectra over the temperature range of 25–100 °C. To explore the buffer trapping effects, the simulated DCT is inspected by varying the activation energy, capture cross section, and concentration of the buffer trap.
Highlights
The GaN buffer layer is intentionally doped with compensational impurity such as iron (Fe) for reducing buffer leakage and punch-through currents, enhancing carrier confinement in the 2DEG and increasing the breakdown voltage of AlGaN/GaN highelectron mobility transistor (HEMT) devices.1–5 The Fe-doping induced acceptor-like traps electrically compensate the residual background donor impurities in the buffer region, thereby resulting in a highly resistive GaN buffer layer.2,5 electron trapping in the buffer promotes current collapse/dispersion, increased ON-resistance (RON) and dynamic shift in threshold voltage, and restricted microwave output power and efficiency, hindering the dynamic operation of the high-electron mobility transistors (HEMTs).1–4 buffer trapping is the major obstacle in the AlGaN/GaN HEMT technology for its successive integration in generation microwave and high-power systems
The Drain Current Transient (DCT) characterization and TCAD simulation studies are carried out to investigate electron trapping in the AlGaN/GaN HEMT with Fe-doped buffer
Two deep-level traps E1 at EC – 0.5 eV and E2 at EC – 0.6 eV are identified in the HEMT from the DCT experiments
Summary
The GaN buffer layer is intentionally doped with compensational impurity such as iron (Fe) for reducing buffer leakage and punch-through currents, enhancing carrier confinement in the 2DEG and increasing the breakdown voltage of AlGaN/GaN highelectron mobility transistor (HEMT) devices. The Fe-doping induced acceptor-like traps electrically compensate the residual background donor impurities in the buffer region, thereby resulting in a highly resistive GaN buffer layer. electron trapping in the buffer promotes current collapse/dispersion, increased ON-resistance (RON) and dynamic shift in threshold voltage, and restricted microwave output power and efficiency, hindering the dynamic operation of the HEMT. buffer trapping is the major obstacle in the AlGaN/GaN HEMT technology for its successive integration in generation microwave and high-power systems. Drain Current Transient (DCT) spectroscopy is a powerful time domain technique to characterize deep-level traps in AlGaN/GaN HEMTs.. Buffer trapping influenced the Y22 parameters, and the drain noise properties of the AlGaN/GaN HEMT were studied through the effective calibration of simulation results with the measured data. Chini et al. identified from the TCAD simulations that the negative peak in the DCT derivative spectra (i.e., decreasing current step in the DCT) is produced due to the hole emission from the acceptor-like trap at EV + 0.9 eV located in the carbon-doped GaN buffer layer. TCAD simulations are performed to investigate the buffer trapping effects on static I–V and DCT characteristics of the HEMT and to identify the physical location of the deep-level traps. The simulated DCT is inspected as a function of buffer trap activation energy, capture cross section, and acceptor concentration to understand the buffer trapping impact on the DCT properties of the AlGaN/GaN HEMT
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