Mohammad A Alim

Temperature-Dependent DC and Small-Signal Analysis of AlGaAs/InGaAs pHEMT for High-Frequency Applications

Temperature-dependent dc and small-signal analysis have been carried out on 0.5 μm × 200-μm AlGaAs/InGaAs pseudomorphic high-electron mobility transistor over the temperature range from -40 °C to 150 °C by on-wafer S-parameter measurements up to 50 GHz. The thermal behavior of dc and equivalent circuit parameters along with their temperature coefficients was analyzed and reported for the first time using the same device. Most of these parameters show a negative trend with temperature, such as drain-source output current I_ds, extrinsic transconductance g_m, effective electron velocity v_eff, threshold voltage V_T, Schottky barrier height φ_b, gate-drain capacitance C_gd, drain-source capacitance C_ds, intrinsic transconductance g_m0, cutoff frequency f_t, and maximum frequency f_max. On the other hand, Two-dimensional electron gas sheet carrier density n_s, ON-resistance R_ON, series resistance R_series, terminal resistances (R_g, R_s, and R_d), output resistance R_ds, input resistance R_i, gate-source capacitance C_gs, and intrinsic delay time τ show a positive trend with temperature. The results provide some valuable insights for future design optimizations of advanced GaAs-based Monolithic microwave integrated circuits.

Temperature dependence of the threshold voltage of AlGaN/GaN/SiC high electron mobility transistors

Shifts in the threshold voltage V T subject to temperature in AlGaN/GaN-based high-electron-mobility transistors (HEMTs) grown on silicon carbide substrate are reported. Variation of V T with drain–source voltage and temperature is investigated, including experimental characterization, modelling and analysis. Possible parameters that affect V T are Schottky barrier height of the device, along with trap-assisted phenomena, aluminium concentration and polarization fields depending on the dielectric, were studied. The threshold voltage and Schottky barrier height shift positively with temperature, and a zero temperature coefficient point in the transfer curve was found before the threshold voltage. An analytical model for threshold voltage V T based on lattice-mismatched Al x Ga1−x N/GaN HEMTs is presented based on aluminium mole concentration, and it is found that V T shifts towards more negative values with increasing aluminium concentration. The model correctly predicts device performance and is found to be consistent with the measured results. These results are valuable for understanding the underlying physics of GaN/SiC HEMTs and their optimization with temperature.

Thermal characterization of DC and small-signal parameters of 150 nm and 250 nm gate-length AlGaN/GaN HEMTs grown on a SiC substrate

This paper investigated the temperature effects on the performance of the AlGaN/GaN high electron mobility transistor (HEMT) with a 150 nm and 250 nm gate length on a SiC substrate over a temperature range of −40 to 150 °C including experimental characterization, modelling and analysis by on-wafer measurements up to 50 GHz. All the DC and small signal parameter variations with ambient temperature on the same set of devices have been reported for the first time. The temperature coefficient of all the DC and small signal parameters as well as f t and f max were reported. Some of the extracted equivalent circuit parameters with the theoretical data of the evolution of electrical parameters and the relevant physical equations involved have been compared using the same biasing condition for further accuracy. The theoretical results are shown to be consistent with the extracted data. Some results are also experimentally verified with previous works cited in the paper. The results provide some valuable insights for the underlying physics of the device parameters affected by temperature.

Thermal Influence on Multibias Small- and Large-Signal Parameters of GaAs pHEMT Fabricated in Multilayer 3-D MMIC

Temperature influence on the device behavior has been carried out on AlGaAs/InGaAs/GaAs-based pseudomorphic high-electron mobility transistor fabricated in multilayer 3-D monolithic microwave integrated circuits technology over multibias operation condition. The multibias thermal effect on the dc and RF, small-signal (up to 40 GHz) and large-signal parameters, including the third-order intercept points as well as the linear and third-order intermodulation output power performance at 4 GHz were analyzed and reported for the first time. In addition, the noise figure parameters of device have been reported and estimated at 10 GHz. The temperature coefficients of the device dc and RF parameters are carefully established at the peak transconductance condition. The results are important for the design optimizations of advanced monolithic multilayer integrations.