Hyungtak Kim

TL;DR: In this paper, a two-dimensional electron gas (2DEG) is induced using the strong spontaneous and piezoelectric polarization inherent in the AlGaN/GaN structures, and three-dimensional nonlinear thermal simulations are made to determine the temperature rise from heat dissipation in various geometries.

TL;DR: In this paper, the dependence of current slump in AlGaN/GaN HEMTs on the thickness of the barrier was observed, with the effect being more pronounced in thin barrier samples.

TL;DR: In this paper, the effects of silicon nitride (SiN) surface passivation and high-electric field stress (hot electron stress) on the degradation of undoped AlGaN-GaN power HFETs were investigated.

TL;DR: In this paper, a photonic high-frequency capacitance-voltage (HF C-V) response of metal-oxide semiconductor (MOS) capacitors is reported for the analysis of interface states in MOS systems.

Abstract: Broad-band high-power cascode AlGaN/GaN high electron-mobility transistor monolithic-microwave integrated-circuit (MMIC) amplifiers with high gain and power-added efficiency (PAE) have been fabricated on high-thermal conductivity SiC substrates. A cascode gain cell exhibiting 5 W of power at 8 GHz with a small-signal gain of 19 dB was realized. A nonuniform distributed amplifier (NDA) based on this process was designed, fabricated, and tested, yielding a saturated output power of 3-6 W over a dc-8-GHz bandwidth with an associated PAE of 13%-31%. A broad-band amplifier MMIC using cascode cells in conjunction with a lossy-match input matching network showed a useful operating range of dc-8 GHz with an output power of 5-7.5 W and a PAE of 20%-33.% over this range. The third-order intermodulation products of the amplifiers under two-tone excitation were studied and third-order-intercept values of 42 and 43 dBm (computed using two-tone carrier power) for the lossy match and NDA amplifiers were obtained.