cElectroluminescence Spectra at Cryogenic Temperatures agree with Ab Initio Calculations of 4H-SiC/SiO2 Interface Defects in a MOSFET

Description

Charge carriers flowing through the channel of a MOSFET can get trapped at SiC/SiO2 interface states affecting the device performance. These states appear due to the lattice mismatch of SiC and SiO2. The density of trapped carriers at the interface can be obtained by measuring the subtreshold sweep hysteresis in the drain current when switching the MOSFET between accumulation and inversion [1]. However, the defect structure at an atomic level still remains an open question despite numerous previous studies. When the atomistic defect types of interface traps are known, the development of defect density reducing techniques is facilitated. Here, we suggest the type and energy position of SiC/SiO2 interface states using energy-resolved electroluminescence measurements at cryogenic temperatures derived from previous works [2, 3] in combination with ab initio calculations. The focus lies on Carbon dangling bonds (PbC) as they have been found with electrically detected magnetic resonance (EDMR) in similar devices [4]. PbC and related vacancy centers can explain the observed emission spectra. The experimental method is based on the spectroscopic measurement of radiative recombinations of charges trapped at defect states. We pulse a 4H-SiC MOSFET between accumulation and inversion resulting in a repeated recombination of electrons and holes with trapped carriers at the interface states. Part of these recombinations emit light, that can be detected by a spectrometer. Fig. 1 shows the experimental setup to switch the gate between accumulation and inversion with a pulse generator, while acquiring the emitted light using a spectrometer. The setup is shaded from ambient light. Since thermal emission of trapped carriers plays a role at room temperature, the spectrum is also measured at 12 K in a cryogenic probe station in order to reduce thermal effects...

Period	14 Sept 2022
Event title	International Confrence on Silicon Carbide and related Materials 2022
Event type	Conference
Location	SwitzerlandShow on map