Type-n electrical activation of ion-implanted P atoms and unintentionally auto-doped N atoms in the CVD diamond films grown on the HPHT Ib substrates, using C2+, Ne2+, Si2+ MeV-ion irradiations

Abstract

The author has succeeded in obtaining n-type electrical conductivity for the P-implanted Chemical Vapor Deposition (CVD) diamond films grown on the High-Pressure High-Temperature (HPHT) type-Ib substrates, annealed by using various MeV-ion irradiations. As-grown CVD diamond films were unintentionally N-auto-doped and inserted from the underlying HPHT Ib substrate during CVD film deposition. P ions were implanted after the growth of CVD films and annealed by 3 MeV C2+ and 4 MeV Si2+ irradiations at 660 °C, and 3 MeV Ne2+ irradiation at 750 °C in vacuum. Auto-doped N atoms were not electrically activated as n-type conductivity just after deposition. However, implanted P atoms and auto-doped N atoms were both electrically activated and exhibited clear n-type conductivity after MeV-ion irradiations. Doping efficiency was achieved around 100% for both implanted P and auto-doped N. The author performed theoretical simulations based on the charge neutrality principle, and the simulated results were fitted to the experimental data of Hall-effect measurements. The author proposed novel electrical activation models for P and N double-doped donor states. These models explain the behaviors of carrier electrons in the conduction band (CB) and subband (SB) at three temperature stages: low, 100–250 °C; middle, 300–450 °C; and high, 500–700 °C. The CB situates upon P-impurity level. Carrier electron movements in the CB and SB are explained, according to mutual excitation and cooling down energy transition procedures between P-, N-impurity levels and CB or SB. The SB might be formed by P implantations and the subsequent MeV-ion irradiations via the assembly of isolated deep trap levels. The author discusses the possibility of MeV-ion irradiations as a novel annealing technology for dopant ion-implanted diamond semiconductors.