dc.description.abstract | ABSTRACT
Deep sub-micron doped-channel heterostructure field-effect transistors (DCFETs) with a high current density and superior microwave power performance was developed and characterized. Due to its excellent current driving capability, Schottky gate performance and thermal stability, it has been widely investigated for microwave power devices and high-speed devices.
A major drawback of DCFETs is their large parasitic source and drain resistances caused by using a high bandgap undoped Schottky layer beneath the gate metal. In this regard, we proposed a method to reduce parasitic resistances by inserting a planar Si δ- doped layer into the InGaP Schottky layer to solve this problem. Furthermore, to achieve a high yield and high uniformity of large area power device crossing the wafer, reactive ion etching was applied to the gate recess process of InGaP/InGaAs doped-channel heterostructure FETs.
Power transistor consumes a lot of dc power and a huge amount of heat will be generated during the operation, this affects the performance and the reliability of devices and circuits. To ensure a stable high power performance of a FET for long-time operation, its evaluation at high temperatures is an essential issue, since large amounts of heat will be generated during the operation. In this study, we will discuss the effect on the dc, rf, and power characteristics between DCFETs and pHEMTs from room temperature (25 C) to 150 C.
A novel Al0.5Ga0.5As/InGaAs enhancement mode pHEMT with a large linear operation range was developed and studied. In order to achieve an enhancement-mode operation in pHEMT design, the thickness of the device Schottky layer is more flimsy than the traditional depletion-mode design. This thin Schottky layer results in the device performance being easily influenced by the surface states, owing to the channel layer closing to the surface. Therefore, we apply the low-k photo- sensitive-benzocyclobutene (BCB) layer to replace the traditional SiNx passivation layer. In addition, BCB passivated layers also reduce the oxidization problem in a high Al mole fraction Schottky layer.
In order to fabricate high performance microwave power transistor for millimeter wave application, sub-micron T-shape gate demonstrated by using e-beam lithography is an efficient method. By using Raith-150 e-beam writer and tri-layer polymer photoresist, the 0.2 µm gate length InGaP/InGaAs DCFET was developed and characterized. Besides, the Curtice large signal model was applied on 0.2 µm gate -length InGaP/InGaAs DCFET. In order to quality the accuracy of the established Curtice model, the device load-pull results which is including power performance, load impendence, are compared with the simulated results on HP advanced design system (HP-ADS) environment.
C-band and K-band MMIC amplifiers based on 0.2 µm gate length InGaP/InGaAs DCFET and BCB passive components have been designed and fabricated. The BCB 3-D MMIC exhibits several benefits including simple process, low parasitic effects for active device, and high circuit robustness. Based on the well-predicted active and passive components, these C-band and K-band MMIC amplifiers were fabricated in our lab. | en_US |