Correlation Among Material Quality, Performance and Reliability of High Power and High Frequency AlGaN/GaN HFET
- PDF / 767,611 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 79 Downloads / 192 Views
1108-A02-04
Correlation among Material Quality, Performance and Reliability of High Power and High Frequency AlGaN/GaN HFET
Nanishi Yasushi Dept. of Photonics, Ritsumeikan Univ., Kusatsu, Shiga 525-8577, Japan
ABSTRACT Performances of AlGaN/GaN HFETs have much improved recently and very high potential of this hetero- structure for high power and high frequency electronic devices has been verified. Application of new device technologies such as field plate, recessed gate, digital predistortion circuit and dual field plate was essential to realize such high device performances both at 2 GHz, 5GHz and 26 GHz. However, practical requirements on the quality and structure of these material systems for production of these devices are still not clear. Extensive studies on correlation among material quality, device performance and reliability were investigated under Japanese NEDO project. Firstly, this paper reviews recent progress of the performances of high power and high frequency AlGaN/GaN HFETs. Then, several interesting results which suggest practical requirements on material quality and structure will be discussed based on our extensive characterization studies in terms of device performances and reliabilities.
INTRODUCTION With its high mobility, high saturation velocity, high breakdown electric field and good thermal conductivity, AlGaN/GaN heterostructure system attracted much attention as a promising material system for high power and high frequency transistors. In contrast with these high potential, actual performances of these devices five years ago were far below the level of those we expected. It was widely understood that the performances of these devices were limited by an undesirable effect of current collapse induced by electron trapping at the surface states of AlGaN. SiN passivasion film on AlGaN top layer decreases this current collapse. However, breakdown voltage decreased and trade off relation between current collapse and breakdown voltage has become apparent. In this paper, several new device technologies applied in this study to solve this problem will be shown, together with recent progress in device and amplifier performances. Then, practical requirements on material quality and structure for production of high performance and good reliable devices will be discussed. RECENT PROGRESS IN DEVICE PERFORMANCES To improve trade off relation between current collapse and breakdown voltage, a recessed gate FET with a field modulating plate (FP) [1, 2] has been developed. Using this
device structure, suppression of current collapse, high voltage operation and improved gain performance have been successfully achieved simultaneously. FP electrode is found to be very effective in suppressing current collapse [3, 4], whereas additional gate recess is effective to further minimize the residual current collapse as well as to increase breakdown voltage with reduced gate leakage current [1, 2, 5]. The gate-drain breakdown voltage defined at 1 mA/mm was improved from 160 V to 200 V after applying recessed str
Data Loading...
