Atomic Configuration
Lattice defects in silicon wafers alter the carrier concentration and decrease lifetime by forming stable clusters of dopants and self-interstitials. The boron interstitial complex consists of a boron atom combined with one or more silicon interstitial atoms. This defect is a dominant cause of performance loss in silicon solar cells and microelectronics.
Defect Generation
Radiation exposure or high-temperature processing dislodges silicon atoms from their regular sites to produce mobile interstitials. These mobile atoms migrate through the crystal lattice until they encounter substitutional boron dopants. The resulting boron interstitial complex creates deep-level trap states within the silicon bandgap.
Once formed, these states act as recombination centers that capture free electrons and holes, reducing the overall diffusion length. This trapping mechanism is highly dependent on both the boron concentration and the injected carrier density.
Electrical Degradation
Minority carrier lifetime in p-type silicon degrades rapidly when these complexes are active. The reduction in lifetime leads to lower open-circuit voltages in photovoltaic devices and increased leakage in transistors. Engineers measure this change using quasi-steady-state photoconductance to monitor the carrier lifetime during light exposure.
Thermal Recovery
Dissociation of the defect requires specific annealing treatments. Heating the silicon wafer to temperatures between two hundred and four hundred degrees Celsius decomposes the boron interstitial complex. This thermal process releases the boron atoms back into active substitutional sites, restoring the initial electrical conductivity of the semiconductor device.
