Kelvin probe force microscopy study of surface potential transients in cleaved AlGaN∕GaN high electron mobility transistors

Abstract

The surface potential of cleaved cross sections of AlGaN∕GaN high electron mobility transistors was measured by Kelvin probe force microscopy. For the bias conditions of Vgs=−5V and Vds=20V, the electric field was concentrated near the GaN∕SiC interface under the gate and between the gate and drain electrodes. A negative potential that decreased over time was observed in the GaN layer beginning 10min after the bias stress was removed. The transient surface potential was found to be well described by an exponential dependence with two time constants: 11 and 55s.

Effects of Traps Formed by Threading Dislocations on Off-State Breakdown Characteristics in GaN Buffer Layer in AlGaN/GaN Heterostructure Field-Effect Transistors

“…To observe the cross-sectional potential distribution of GaN with a thickness of 2 m, the sample was cleaved and then set vertically upward on a sample holder. Details of the measurements were described 12) Figure 4 shows a cross-sectional image of the potential distribution with an anode bias of þ20 V. The V TFL of this cleaved sample was 23 V. 13) As shown in Fig. 4, the equipotential lines are perpendicularly aligned to the substrate near the surface, whereas those near the interface between the epilayer and the substrate are nearly parallel to the substrate.…”

Effect of Source–Drain Opposite Side Gate on the AlGaN/GaN High Electron Mobility Transistor Devices

“…Numerous literature reports suggest that the formation of a virtual gate due to surface state electron capture between the gate and drain is the main mechanism causing the current collapse effect. [22][23][24][25] To effectively suppress the current collapse effect, it is necessary to fundamentally reduce the impact of the virtual gate formed by the AlGaN layer on the device. In the traditional T-type gate structure, the virtual gate effect is formed due to the influence of thermal effects, where electrons tunnel to the AlGaN surface and are captured by surface states, leading to energy loss and an increase in leakage current density, ultimately resulting in device failure.…”

Evaluation of electroluminescence of AlGaN/GaN HEMT on free-standing GaN substrate

“…[8][9][10] Previous literatures employed Kelvin force microscopy, Raman microscopy, or electroluminescence (EL) to evaluate the correlation between the current collapse and the electric field distribution in HEMTs. [12][13][14] Among these methods, EL is a simple and non-destructive method to indicate an area of the highest electric field. [14][15][16][17][18][19][20][21][22][23] So far, the EL in HEMTs has been investigated in terms of dependency of a device structure, including kinds of a passivation layer, with and without a GaN cap, and distance of gate-to-drain (L gd ).…”