Temperature and Bias Dependent Trap Capture Cross Section in AlGaN/GaN HEMT on 6-in Silicon With Carbon-Doped Buffer

We report on the estimation of trap capture cross section in AlGaN/GaN HEMTs as a function of bias and temperature. Conductance dispersion technique was employed to study the AlGaN/GaN interface of the devices with a carbon-doped GaN buffer grown on 6-in silicon. While a negligible shift in the threshold voltage (<inline-formula> <tex-math notation="LaTeX">$V_{\mathrm {{\textsf {TH}}}}$ </tex-math></inline-formula>) was observed in temperature-dependent <inline-formula> <tex-math notation="LaTeX">$I_{\mathrm {{\textsf {DS}}}}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$V_{\mathrm {{\textsf {GS}}}}$ </tex-math></inline-formula> sweeps, we observed a spread in the capacitance-voltage (<inline-formula> <tex-math notation="LaTeX">$C$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula>) measurements, indicating a contribution of interface traps. When biased near depletion, G/<inline-formula> <tex-math notation="LaTeX">$\omega $ </tex-math></inline-formula> versus frequency plot for AlGaN/GaN interface exhibits two peaks which correspond to a pair of trap density (<inline-formula> <tex-math notation="LaTeX">$D_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula>) and trap time constant (<inline-formula> <tex-math notation="LaTeX">$T_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula>) values. This was explained using a circuit model in conjunction with energy band diagram. The <inline-formula> <tex-math notation="LaTeX">$D_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$T_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula> values for one peak were in the range from ~ 0.3–<inline-formula> <tex-math notation="LaTeX">$7\times 10^{12}$ </tex-math></inline-formula>/eV <inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm<sup>2</sup> and 0.6–<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{s}$ </tex-math></inline-formula> while for the other peak, <inline-formula> <tex-math notation="LaTeX">$D_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$T_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula> were in the range of ~0.1–<inline-formula> <tex-math notation="LaTeX">$35\times 10^{12}$ </tex-math></inline-formula>/eV <inline-formula> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> cm<sup>2</sup> and ~0.06–<inline-formula> <tex-math notation="LaTeX">$0.3~\mu \text{s}$ </tex-math></inline-formula> at 25 °C. From the <inline-formula> <tex-math notation="LaTeX">$T_{\mathrm {{\textsf {it}}}}$ </tex-math></inline-formula> values, electron capture cross section (<inline-formula> <tex-math notation="LaTeX">$\sigma )$ </tex-math></inline-formula> for both the traps was extracted and was found to be decreasing with increasing temperature in the range of <inline-formula> <tex-math notation="LaTeX">$1.1\times 10^{-20}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$1\times 10^{-19}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\mathrm {{\textsf {2}}}}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$4.5\times 10^{-20}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$1\times 10^{-17}$ </tex-math></inline-formula> cm<sup>2</sup> for slow traps and fast traps, respectively. A multiphonon emission effect was invoked to explain the temperature dependence of capture cross section.