Study Of AlGAN/GAN HEMT Model And Design Of MMIC Power Amplifiers

With rapid development of microwave communication and aviation technology, it set high demands on semiconductor device with higher work frequency and output power. Due to the limit of material parameters, the performance of traditional microwave power transistor based on Si and GaAs can't improved further, while wide band gap semiconductor material such as GaN and SiC, devices with these materials can satisfy the system need of high frequency, high output power, and high temperature. It has recently become the focus of research. For its advantages in the frequency, power consumption, and noise, HEMT MMIC is one of the most competitions in the fields of micro-millimeter wave monolithic integrated circuits and super-high velocity digital integrated circuits. In this paper, the key content is AlGaN/GaN HEMT model and design of MMIC, the concrete studies are lised as follows.1. Based on the analysis of the device structure and working mechanism of AlGaN/GaN HEMT, the device characteristics are analyzed, the effects of elevated temperatures on low-field mobility and threshold voltage are investigated. A temperature dependent analytical model has been presented for AlGaN/GaN HEMT to simulate the DC I-V performance. In this model the effects of polarization, materials thermal conductivity, electron mobility, sheet carrier density, velocity saturation, conduction band discontinuity are taken into consideration. The comparison between simulations and measurements shows a good agreement, it is prove that this model is accurate and can simulate the DC I-V performance of AlGaN/GaN HEMT for SiC and sapphire substrate2. In this paper, the GaN MNIC active and passive components model are studied. The method of parameter extraction for HEMT small-signal equivalent circuit is derived comprehensively and scientifically. Several familiar models for capacitances and large signal I-V characteristics of AlGaN/GaN HEMT are discussed. Based on EEHEMT1 model, using the on-wafer measurement system and the narrow pulse testing technology, the AlGaN/GaN HEMT nonlinear model is established and compared with measurements data. The experimental results agree closely with simulated results.3. The technology and principal performance parameter of HEMT broadband MMIC power amplifier is researched. Based on distributed technology combined with reactively matched method, the two-stage broadband MMIC power amplifiers are designed. Adoptting low-pass matching networks, the amplifiers are designed to fully match 50 ohm input and output impedance. Operating frequencies from 7 GHz to 13 GHz, output power is above 17W, typical output power is above 18 dB, max output power is 25W, power added efficiency PAE reached 29.9%.