Characterization of hole traps in reverse-biased Schottky-type p-GaN gate HEMTs by current-transient method

Abstract

In this study, the current-transient method has been conducted to investigate the trap states in p-GaN gate high-electron-mobility transistors (HEMTs) under reverse gate stress. An irregular threshold voltage shift under reverse gate bias has been observed through the pulsed transfer measurements with different delay times. It suggests that both the hole insufficiency and hole trapping are generated during the reverse gate pulse bias. With proper selection of the delay time based on the pulsed characterizations, the hole detrapping can be effectively evaluated after the hole recovery is completed. In addition, by subtracting the trapping behavior caused by the measurement condition, the actual detrapping transient under reverse gate filling voltages can be obtained with the current-transient method. Three traps have been observed with the energy levels of 0.484, 0.390, and 0.235 eV. The identification of hole traps may provide a basis on the understanding of threshold voltage instability and further improvement of the reliability of p-GaN gate HEMTs.

Formation of Grown-In Nitrogen Vacancies and Interstitials in Highly Mg-Doped Ammonothermal GaN

“…The parameters determined from the Arrhenius plot for the T1 trap well match those for the hole trap DP1, with the activation energy and pre-exponential factor of E v + 484 meV and 1.77 × 10 4 K −2 s −1 , respectively, detected by the current transient method in the p -type GaN film playing role a gate in a high-electron-mobility transistor (HEMT) [ 39 ]. This trap, similarly to the other hole traps found in a p -GaN HEMT and p -GaN Schottky diodes with the E a of 480–490 meV and A in the range of 10 3 –10 4 K −2 s −1 , was suggested to be attributed to nitrogen vacancies [ 40 ].…”

Trap Characterization Techniques for GaN-Based HEMTs: A Critical Review

“…where σ n is the electron capture cross-section, γ n contains the density and thermal velocity of electrons, E a is the trap activation energy, and k B is the Boltzmann constant [51]. From the perspective of characterization methods, DCT, LFN, and low-frequency output admittance methods are used more frequently to characterize traps in semiconductor bodies, while other methods such as C-V and dispersion of conductance output are mainly used to characterize the traps at semiconductor interfaces.…”

“…The drain current transient (DCT) test involves applying large positive V ds bias, large negative V gs bias, or both to measure the change in I DS [48][49][50][51][52][53][54][55][56]. The transient current I DS can be expressed as…”

“…where ∆I i is the amplitude, τ i is the time constant of the trap, and I ∞ is the current which is at a steady state [51]. The Bayesian deconvolution method can be used to obtain the time constant of traps (τ n ) and the energy level and cross-section of the trap can be derived from Arrhenius plots:…”

Gate-Bias Induced RON Instability in p-GaN Power HEMTs

“…EVERAL studies are present in the literature that involve the investigation of the stability of normally-off p-GaN high electron mobility transistors (HEMTs) after applying gate bias stress [1]- [9]. These studies mostly focus on the instability of the threshold voltage (VT) [2], [4]- [10] caused by dynamic effects occurring at (or near) the device region under the gate [11].…”