The potential advantage of industrially processed boron emitters compared to phosphorus emitters

Abstract

A boron emitter that is transferrable to mass production is compared to a phosphorus emitter of industrial standard and a phosphorus emitter with reduced phosphorus concentration, on the viewpoints of the doping profiles, emitter saturation current (J0E), and internal quantum efficiency at shorter wavelength (= blue IQE). The doping profiles are characterized considering active and inactive dopant, and including the doping source before HF treatment. We found boron atoms are segregated towards the doping source while phosphorus segregates towards the emitter, which could explain the absence of inactive dopant in boron emitters as opposed to a substantial amount of inactive dopant in phosphorus emitters. It was also found that inactive phosphorus is still present even down to 1×1019 cm-3 also for the lightly doped emitter. The boron emitter showed the highest blue IQE probably due to the absence of both inactive dopant and heavy doping above 1×1020 cm-3. On the other hand, 10 mV Voc gain of the phosphorus emitters by decreasing J0E from 180 to 45 fA/cm2 implied the possibility of Voc improvement also for the boron emitter by reducing J0E which is 97 fA/cm2 at present.