Electrical properties/Doping efficiency of doped microcrystalline silicon layers prepared by hot-wire chemical vapor deposition

Abstract

Microcrystalline silicon (μc-Si) doped films were prepared by hot-wire chemical vapor deposition (HWCVD) to investigate the doping efficiency. The incorporation probability of different dopant atoms into the solid-phase is always increasing with the doping gas concentrations, but very different for the doping gases used: trimethylboron (TMB), boron trifluoride (BF 3) and phosphine (PH 3). At the same doping gas concentration in the process gas the incorporation of phosphorus atoms into the solid μc-Si phase is much larger than that of boron atoms with respect to the dissociation probability of the doping gases. The electron and hole concentrations, estimated from Hall measurements, are directly related to the solid phase concentration of the doping atoms and independent of the type of dopant and the doping gas used. This results in an equal doping efficiency of about 20 % for the incorporated B and P atoms in doped HWCVD μc-Si films. For the dopant atom concentration regime investigated the doping efficiency of B atoms is in good agreement with corresponding PECVD doping efficiencies however, the doping efficiency of P atoms is considerably lower for our n-doped films.