Influence of emitter profile characteristics on thermal stability and passiviation quality of a-Si/SiNX-passivated boron emitters

We present emitter saturation current densities (J0E) of different types of BBr3 furnace-diffused boron emitters for a range of different sheet resistances on planar an textured surfaces: (a) “oxidized” emitters with an extended drive-in phase under oxygen and (b) “industrial” emitters without such additional drive-in step. Upon passivation with amorphous silicon - silicon nitride (a-Si/SiNX) stacks on planar surfaces we measure the J0E as a function of annealing time at 500 and 600°C respectively. The oxidized boron emitters show thermal stability up to 600°C with a stable J0E of 13 ± 2 fA/cm² for 90 Ω/□. This is comparable to p⁺ emitter performance after passivation by ALD-deposited Al2O3. The ”industrial type” 90 Ω/□ emitter shows a J0E of 47 ± 5 fA/cm2 after annealing at 600°C due to a higher boron surface concentration and enhanced recombination within the emitter volume. Our a-Si/SiNX passivated emitters on textured surfaces exhibit about 50% higher J0E values than emitters on planar surfaces, which corresponds well with the increased area of the KOH-textured wafers.