cElectroluminescence Spectra at Cryogenic Temperatures agree with Ab Initio Calculations of 4H-SiC/SiO2 Interface Defects in a MOSFET
Sprache des Vortragstitels:
Englisch
Original Tagungtitel:
International Confrence on Silicon Carbide and related Materials 2022
Sprache des Tagungstitel:
Englisch
Original Kurzfassung:
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...
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