Huang Sen

Optimized power simulation of AlGaN/GaN HEMT for continuous wave and pulse applications*

An optimized modeling method of 8 × 100 μ m AlGaN/GaN-based high electron mobility transistor (HEMT) for accurate continuous wave (CW) and pulsed power simulations is proposed. Since the self-heating effect can occur during the continuous operation, the power gain from the continuous operation significantly decreases when compared to a pulsed power operation. This paper extracts power performances of different device models from different quiescent biases of pulsed current-voltage ( I-V ) measurements and compared them in order to determine the most suitable device model for CW and pulse RF microwave power amplifier design. The simulated output power and gain results of the models at V gs = -3.5 V, V ds = 30 V with a frequency of 9.6 GHz are presented.

AlGaN/GaN high electron mobility transistor with Al2O3+BCB passivation

In this paper, A12O3 ultrathin film used as the surface passivation layer for Al Ga N/Ga N high electron mobility transistor(HEMT) is deposited by thermal atomic layer deposition(ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition(PECVD) Si N passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency(RF) performance are achieved after applying Al2O3+BCB passivation.For the Al2O3+BCB passivated device with a 0.7 μm gate, the value of f max reaches up to 100 GHz, but it decreases to 40 GHz for Si N HEMT. The f max/ f t ratio(≥ 4) is also improved after Al2O3+BCB passivation. The capacitance–voltage(C–V) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states(on the order of magnitude of 1010cm-2) than that obtained at commonly studied Si N HEMT.In this paper, A12O3 ultrathin film used as the surface passivation layer for AlGaN/GaN high electron mobility transistor (HEMT) is deposited by thermal atomic layer deposition (ALD), thereby avoiding plasma-induced damage and erosion to the surface. A comparison is made between the surface passivation in this paper and the conventional plasma enhanced chemical vapor deposition (PECVD) SiN passivation. A remarkable reduction of the gate leakage current and a significant increase in small signal radio frequency (RF) performance are achieved after applying Al2O3+BCB passivation. For the Al2O3+BCB passivated device with a 0.7 μm gate, the value of fmax reaches up to 100 GHz, but it decreases to 40 GHz for SiN HEMT. The fmax/ft ratio (≥ 4) is also improved after Al2O3+BCB passivation. The capacitance–voltage (C–V) measurement demonstrates that Al2O3+BCB HEMT shows quite less density of trap states (on the order of magnitude of 1010 cm−2) than that obtained at commonly studied SiN HEMT.

Device physics towards high performanceGaN-based power electronics

Gallium-nitride-based power electronic devices, with the inherent high breakdown voltage, high working frequency, high output current density and high temperature operating capability, are promising candidates for next-generation high-efficiency and compact power management systems. In this work, the scientific and technical challenges towards high-performance GaN power devices, including threshold voltage instability, dynamic ON-resistance degradation, enhancement-mode gate techniques and long-term reliability of gate dielectrics, are investigated based on in-depth analysis of the physical origin of interface states and high-voltage current collapse. Oxidation of (Al) GaN surface are suggested to be the primary cause for the surface/interface states in GaN-based power devices. State-of-the-art device technologies, including nitridation-interficial-layer to suppress dielectric/(Al) GaN interface oxidation, polarized PEALD-AlN passivation for compensation of deep interface states, E-mode techniques of fluorine plasma ion implantation and high-temperature low-damage gate-recess, high-breakdown-strength LPCVD-SiN x and O3-sourced ALD-Al2O3 gate dielectrics are introduced for fabrication of high performance and reliability GaN-based power electronic devices.