研究目的
To investigate the origin of the defects causing light and elevated temperature induced degradation (LeTID) in high purity monocrystalline silicon using float-zone silicon under more defined conditions.
研究成果
The experiments on FZ silicon have independently confirmed several observations from mc and Cz silicon under more defined conditions. The high purity of the material allowed for interesting observations that might have been missed or discarded on less pure material. The findings open interesting pathways for future research.
研究不足
The absence of a detectable degradation in the n-type samples and the minute concentrations of additional hydrogen introduced during the specific process performed are noted as limitations. Future experiments with an optimized temperature profile are planned.
1：Experimental Design and Method Selection:
The study involved a series of experiments on float-zone silicon wafers of both p- and n-type doping to investigate LeTID. Different surface passivation schemes based on aluminium oxide layers were combined with a designated hydrogenation treatment and subjected to different thermal processes.
2：Sample Selection and Data Sources:
FZ silicon wafers of both p- and n-type doping featuring a resistivity of 1 ?cm, 4” diameter and a thickness of 250 μm (p-type) and 200 μm (n-type) were used.
3：List of Experimental Equipment and Materials:
Samples were passivated by Al2O3 layers deposited via atomic layer deposition (ALD) in an Oxford Instruments OpAL reactor. Some samples received a 100 nm thick a-SiNx capping layer deposited in an industrial PECVD reactor.
4：Experimental Procedures and Operational Workflow:
After wet chemical cleaning, a part of the samples was subjected to an annealing under hydrogen plasma at 500 °C. The passivated samples were either subjected to “fast firing” in an industrial belt firing furnace (FFO) or “slower” profiles in a rapid thermal processing (RTP) furnace.
5：Data Analysis Methods:
Effective carrier lifetimes τeff were measured with a WCT-120 Sinton Instruments Lifetime Tester? in transient mode evaluated at a minority charge carrier density (MCD) of 2·1014 cm-3. Photoluminescence imaging (PLI) was performed at most time steps and at various intensities.
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