Abstract:Minority-carrier lifetime is one of the key parameters governing the performance of semiconductor devices. Here, we report on tuning the minority-carrier lifetime through stacking fault (SF) defects in polytypic SiC. The SFs are distinguished in terms of their characteristic luminescence peaks at 482 nm, 471 nm, and 417 nm, respectively. Different from general point, linear, and volume defects, the planar SFs demonstrate the interesting phenomena of either decreasing or increasing the minority-carrier lifetime… Show more
“…In this context, we investigate stacking faults (i.e. polytypic inclusions in 4H-SiC) as an intrinsic quantum well forming mechanism 35–37 , and the effects that these structures have on divacancy defect (two adjacent empty atomic sites) color centers in their vicinity.Fig. 2Common SiC polytypes and structure of a stacking fault in 4H-SiC. a – c show the primitive cells, the stacking sequences, and the possible divacancy nonequivalent configurations in 4H, 6H, and 3C-SiC, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…2b) inclusion in a 4H-SiC crystal 37,38 . It has been shown that such stacking faults form quantum-well-like states that have been observed through photoluminescence (PL) 35–37 measurements in which the 6H in 4H polytypic inclusion was typically identified using the 482 nm PL-emission line 37 .…”
Section: Resultsmentioning
confidence: 99%
“…Stacking faults and polytype inclusions are natural sources of quantum wells in semiconductors (21)(22)(23). Such extended defects may additionally incorporate color centers that can exhibit distinct properties compared to their bulk counterparts (24).…”
Defect-based quantum systems in wide bandgap semiconductors are strong candidates for scalable quantum-information technologies. However, these systems are often complicated by charge-state instabilities and interference by phonons, which can diminish spin-initialization fidelities and limit room-temperature operation. Here, we identify a pathway around these drawbacks by showing that an engineered quantum well can stabilize the charge state of a qubit. Using density-functional theory and experimental synchrotron X-ray diffraction studies, we construct a model for previously unattributed point defect centers in silicon carbide as a near-stacking fault axial divacancy and show how this model explains these defects’ robustness against photoionization and room temperature stability. These results provide a materials-based solution to the optical instability of color centers in semiconductors, paving the way for the development of robust single-photon sources and spin qubits.
“…In this context, we investigate stacking faults (i.e. polytypic inclusions in 4H-SiC) as an intrinsic quantum well forming mechanism 35–37 , and the effects that these structures have on divacancy defect (two adjacent empty atomic sites) color centers in their vicinity.Fig. 2Common SiC polytypes and structure of a stacking fault in 4H-SiC. a – c show the primitive cells, the stacking sequences, and the possible divacancy nonequivalent configurations in 4H, 6H, and 3C-SiC, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…2b) inclusion in a 4H-SiC crystal 37,38 . It has been shown that such stacking faults form quantum-well-like states that have been observed through photoluminescence (PL) 35–37 measurements in which the 6H in 4H polytypic inclusion was typically identified using the 482 nm PL-emission line 37 .…”
Section: Resultsmentioning
confidence: 99%
“…Stacking faults and polytype inclusions are natural sources of quantum wells in semiconductors (21)(22)(23). Such extended defects may additionally incorporate color centers that can exhibit distinct properties compared to their bulk counterparts (24).…”
Defect-based quantum systems in wide bandgap semiconductors are strong candidates for scalable quantum-information technologies. However, these systems are often complicated by charge-state instabilities and interference by phonons, which can diminish spin-initialization fidelities and limit room-temperature operation. Here, we identify a pathway around these drawbacks by showing that an engineered quantum well can stabilize the charge state of a qubit. Using density-functional theory and experimental synchrotron X-ray diffraction studies, we construct a model for previously unattributed point defect centers in silicon carbide as a near-stacking fault axial divacancy and show how this model explains these defects’ robustness against photoionization and room temperature stability. These results provide a materials-based solution to the optical instability of color centers in semiconductors, paving the way for the development of robust single-photon sources and spin qubits.
“…Table 1 lists the experimental and theoretical results of phase transformation in SiC under different conditions. Since the 3C polytype introduces a quantum well (QW) structure in the 4H structure [4,8,37], energy would be gained through electrons entering the QW-related states, which is energetically favourable for the 4H ! 3C phase transformation during high-temperature annealing (>1000°C) [23,38].…”
“…Lifetime decrease with nitrogen doping, not correlating with the Z 1/2 trap density, was also observed in [7]. The recombination mechanisms when intrinsic Z 1/2 trap density is negligibly low are often attributed to surface recombination, dislocations and stacking faults [8][9][10][11]. Few works also indicate that other point defects cannot be neglected [2,12].…”
Carrier dynamics in n-type 4H-SiC epilayers of varying thicknesses and low Z1/2 defect concentrations are investigated here in wide ranges of excess carrier density and temperature. Several techniques are employed to monitor carrier diffusion and recombination processes, including light induced transient grating (LITG), microwave photoconductance decay (MPCD) and free carrier absorption (FCA) using ps-laser pulses at 355 nm. The observed increase of the diffusion coefficient with the increasing excitation level is explained by the transition from the minority to the bipolar transport regime. Its subsequent decrease with even higher excitations is found to be governed by band-gap renormalization and degeneracy effects. The bulk lifetime, limited by hole traps at 0.19–0.24 eV above the valence band at lower excitations, was found to decrease from few microseconds to hundreds of nanoseconds during the transition regime from the minority to the bipolar transport. Our temperature-dependent measurements confirmed the trap activation energy and provided the approximate functional form of electron and hole lifetimes as τe = 340 × (T/300 K)3/2 ns and τh = 100 × (T/300 K)–1/2 ns, for the temperature T range 80–800 K. It was found to hold for 65 and 120 μm sample thicknesses, while the lifetimes were found to be twice shorter for the sample 35 μm thick.
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