VACANCIES AND IMPURITIES IN INP STUDIED USING POSITRON LIFETIME AND AN IMPROVED DOPPLER-BROADENING SPECTROMETER

Positron lifetime and Doppler-broadening measurements are used to inve stigated defects in as-grown InP materials. Positron trapping by vacan cies is found in all of the InP samples examined, regardless of conduc tion type and carrier concentration, we discover that the positron lif etime is more dependent on the conduction type than on the carrier con centration. In the n- and SI-type InP, the positron average lifetimes are all found to be around 247 ps, but in p-InP the average is 4 ps lo wer at 243 ps. We attribute this difference to the different trapping centers in p-InP compared with n- and SI-InP samples. By using the tem perature dependence of positron lifetimes, we also observe the negativ ely charged impurity centers Zn, in Zn-doped p-InP. The line-shape par ameter measured by an improved Doppler-broadening spectrometer shows a significant difference between n-type and Fe-doped SI-InP materials: the S-parameter varies from 0.5203 in n-InP to 0.5184 in Fe-doped SI-I nP by four times the standard deviation. A possible reason for this di fference is discussed.