GaN HEMT yapılarının üretimi, modellenmesi ve ölçümü, ve yüksek güçlü MMIC yükselteçlerin tasarımı

High power and high frequency requirements in advanced telecommunication systems become more stringent as faster and higher capacity wireless data transfer over long distances is getting a common need for both military and commercial applications. Present mature semiconductor technologies have already reached their performance limits in responding next generation needs of high power modules. Under these circumstances, further improvements seem to be possible via introducing more capable technology. GaN HEMT device technology promises high power performance in microwave and millimeter-wave regimes at least an order of magnitude better than any other current counterparts. Research and development processes of this technology require deep understanding of theoretical fundamentals of HEMT device formation and should be supported by efficient epitaxial wafer growth and microfabrication facilities, and accurate large-signal nonlinear modeling capability. After all, GaN HEMT technology can be transformed to real applications of monolithic microwave integrated circuit (MMIC) power amplifiers (PAs).This work can be separated into three main parts. In the first part, we introduced bottom up approach to the GaN HEMT technology starting from GaN material properties, semiconductor physics and design of GaN HEMT devices, and MOCVD growth and characterization, completing with fabrication processes and large-signal nonlinear modeling issues of the active devices. 2DEG sheet carrier concentrations in the order of 1xE13 cm-2 and electron mobility values between 1500-2000 cm2/V?s are obtained from our GaN HEMT epiwafers. Furthermore, 900mA/mm of maximum drain current density, 32GHz of fT, and 40 GHz of fmax are achieved from a fabricated 6x150um GaN HEMT device. Large-signal nonlinear modeling is applied successfully for a 4x200um device with 1um gate length. In the second part, this model is used as a basis for two MMIC PA designs have center frequency of 2GHz and coplanar wave guide passive elements. ~2W and ~4W output power levels and ~42% and ~35% PAE values are generated from these MMIC PAs at 1dB compression point, respectively. In the final part, we applied our MMIC PA design experiences to a GaAs pHEMT process of UMS foundry. We introduced two-stage balanced PA topology in order to achieve wideband and high power response at the output. Aimed frequency range is 18-22GHz. According to the simulation results, output power of ~2W is obtained with 31%-35% PAE in this frequency band. S-parameter measurement data are quite in agreement with simulation results, even better. CW power measurement results are subjected to 1-2dB degradation in output power levels compared to HB simulation results since the design kit we used contains pulsed measurement based transistor models. The measurements results proved the efficiency and correctness of our design.Keywords: GaN HEMT, MMIC PA design, MOCVD growth, microfabrication, large-signal nonlinear modeling, K-band balanced MMIC PA design, GaAs pHEMT.