It was recalled that highly n+-doped sub-collector layers in such heterojunction bipolar transistor structures led to markedly enhanced Zn diffusion in the subsequently grown base layer. It was shown that this abnormal Zn diffusion could be suppressed by interrupting growth before the Zn-doped layer was grown. It was speculated that this interruption of growth permitted excess non-equilibrium group-III self-interstitials, coming from the n+-doped sub-collector layer, to disappear before they could enhance Zn diffusion in the base layer.

T.Kobayashi, K.Kurishima, U.Gösele: Applied Physics Letters, 1993, 62[3], 284-5