Thermal Admittance Spectroscopy of AlGaN/GaN HEMT Structure

Thermal Admittance Spectroscopy (TAS) is the most reliable method to analyze the effect of traps in wide band gap semiconductor devices such as AlGaN/GaN HEMTs. The increase or decrease in admittance at different frequencies and temperatures will reveal the occupation of defects present within the AlGaN/GaN HEMT structure. Therefore, the TAS method is utilized in this work to measure the activation energy of traps in AlGaN/GaN HEMTs using admittance-frequency measurements over a temperature range. In this work, we have used three different devices: device1 (D1), device2 (D2), and device (D3). D1 has 0.5 \(\upmu \text {m}\) gate length with 3.6 \(\upmu \text {m}\) source-drain spacing on a Si substrate obtained from MACOM. D2 from CREE has 0.4 \(\upmu \text {m}\) gate length with 3 \(\upmu \text {m}\) gate-drain spacing on 100-mm semi-insulating 4H silicon carbide substrate. In-house fabricated D3 AlGaN/GaN Heterostructure was grown on SiC Substrate. The thermal admittance spectroscopy indicates the respective activation energy and capture cross-section for these devices as D1( ~0.35 eV, ~ 6.5 \(\,\times \,\) 10-15 cm2), D2( ~0.27 eV, ~ 5.9 \(\,\times \,\) 10-20 cm2 ) and D3( ~0.12 eV, ~ 1.2 \(\,\times \,\) 10-21 cm2).