Electrically stimulated optical spectroscopy of interface defects in wide-bandgap field-effect transistors

Abstract

Wide-bandgap semiconductors such as silicon carbide, gallium nitride, and diamond are inherently suitable for high power electronics for example in renewable energy applications and electric vehicles. Despite the high interest, the theoretical limit regarding device performance has not yet been reached for these materials. This is often due to charge trapping in defects at the semiconductor-insulator interface. Here we report a one-to-one correlation between electrically stimulated photon emission and the threshold voltage shift obtained from a fully processed commercial 4H-SiC metal-oxide-semiconductor field-effect power transistor. Based on this observation, we demonstrate that the emission spectrum contains valuable information on the energetic position of the charge transition levels of the responsible interface defects. We etch back the transistor from the reverse side in order to obtain optical access to the interface and record the emitted light. Our method opens up point defect characterization in fully processed transistors after device passivation and processing. This will lead to better understanding and improved processes and techniques, which will ultimately push the performance of these devices closer to the theoretical limit.

Assessing, Controlling and Understanding Parameter Variations of SiC Power MOSFETs in Switching Operation

“…This spectrum can be understood as a fingerprint of the radiative electronic interface transitions with distinct peak energies. The target of future research will be to further refine this optical methodology and to correlate the characteristic peaks in the spectrum to defect types suggested by theoretical calculations [9,10]. Also, correlating defect-specific emission peaks to findings of alternative methods that provide structural defect information such as electrically detected magnetic resonance [19,20] could lead to a deeper understanding of the nature of the involved defects.…”

Electroluminescence Spectra of a Gate Switched MOSFET at Cryogenic and Room Temperatures Agree with Ab Initio Calculations of 4H-SiC/SiO₂-Interface Defects

“…Aside from room temperature measurements, which have been already investigated in [4,5], we also conducted experiments at cryogenic temperatures to investigate the impact of reduced thermal energy onto the radiative process and to ease defect identification. Once a charge carrier is trapped in a defect state, the branching ratio of radiative versus non-radiative detrapping increases.…”

“…When the atomic defect configurations of interface traps are known, the development of defect density reducing techniques is facilitated. Here, we use energy-resolved electroluminescence measurements [3,4,5,6] at cryogenic temperatures in combination with ab initio calculations to characterize the SiC/SiO 2 -interface. During the measurement the gate is switched between accumulation and inversion which results in radiative carrier recombinations via mid gap defects.…”

Editors’ Choice 2023

“…Measuring point defects at the interface after fabrication often involve destroying the delicate device architecture or fabricating dedicated test structures to investigate the interface. An article by Feil et al 3 published a clever alternative in Communications Engineering , etching back the device substrate to spectroscopically probe the field-effect stimulated radiative defect transitions from the underside of wide-bandgap semiconductor metal-oxide-semiconductor field-effect transistors. A contrast between their approaches and those of previous works can be found in Fig.…”

“…1 Illustration of optical top-side detection (approach reported in previous studies) and reverse-side detection (approach reported here). Reused from 3 . …”