RF Performance and Reliability of SiC MESFETs on High Purity Semi-Insulating Substrates

Abstract

In this paper we report on our efforts to reduce trap effects, increase efficiency, and improve the yield and reliability of SiC MESFETs. By minimizing substrate and surface-related trapping effects that have previously been observed in SiC MESFETs, drain efficiencies as high as 68% have been achieved at 3.5 GHz with associated CW power densities of 3.8 W/mm. MESFETs fabricated with this process have passed 1,000 hour High Temperature Reverse Bias test (HTRB) with negligible change in dc or RF parameters. A sampling of these devices have also been running for over 2,000 hours in an RF high temperature operating life test (HTOL) with negligible change in parameters. This MESFET process has been transferred to 3-inch high purity semiinsulating (HPSI) substrates. The quality of this process is demonstrated by the cross-wafer uniformity of the breakdown voltage and a standard deviation in gate threshold voltage of 0.6 V.

Present Status and Future Prospect of Widegap Semiconductor High-Power Devices

“…26) In addition, Sriram et al performed a lifetime test at a junction temperature of 240 C using an SiC MESFET, and they reported a linear gain degradation of 0.3 dB and a saturation power degradation of 0.4 dB even after 700 h operation, which means that the device reliability does not have any problem. 27) Besides these types of devices, the fabrication of an impact ionization avalanche transit-time (IMPATT) diode was also reported with a peak output power of 1.8 W (11.8 GHz), aiming at applications in the millimeterwave region. 28)…”

SiC MESFETs for High-Frequency Applications

“…6,7 The results of these tests indicate that the *The adjacent-channel power ratio is the ratio of the power in the main channel to the power in an adjacent communication channel produced by distortion in the main channel. 6,7 The results of these tests indicate that the *The adjacent-channel power ratio is the ratio of the power in the main channel to the power in an adjacent communication channel produced by distortion in the main channel.…”

Conductance Deep-Level Transient Spectroscopic Study of 4H- SiC MESFET and Traps

“…Over the past few years, the vanadium-doped semi-insulating SiC substrate has attracted much attention in explaining the deterioration of the SiC MESFET microwave performance. Recently, the concern has shifted more towards surface traps due to the introduction of high-purity semi-insulating substrates, which have eliminated the larger part of the problems associated with the substrate [8,9]. The presence of surface states in the ungated channel regions between drain and source terminals has modulated the depletion of the channel under the device surface, and has resulted in the frequency dispersion of the transconductance (gm) and gate lag transient [10,12].…”