Efficient visible photoluminescence in the binary a-Si:Hx alloy system

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Abstract
We report the photoluminescence (PL) and structural properties of a new class of efficient visible‐light‐emitting semiconductors: low defect density a‐Si:Hx alloys. For films prepared by the (thermal) homogeneous chemical vapor deposition (HOMOCVD) method, new broadband PL develops for x>0.3, reaching a peak emission energy of 2.05 eV for a hydrogen content x=0.66 (40 at. % H). We attribute the wide gaps to the influence of Si–H bonding on the density of states near the valence band edge. We ascribe the new PL process to band‐to‐band recombination from within the alloy band tails. This emission persists at room temperature with an integrated intensity comparable to conventional light‐emitting diode (LED) materials. Qualitatively similar results are obtained for low‐temperature‐deposited rf plasma films prepared from Si2H6, but not from SiH4. We show that a low Si dangling bond concentration is the key factor, for all the different film types, to achieving efficient luminescence.