Neutron transmutation doping of isotopically engineered Ge

• Published in: Applied physics letters Vol. 64; no. 16; pp. 2121 - 2123
• Main Authors: Itoh, K. M., Haller, E. E., Hansen, W. L., Beeman, J. W., Farmer, J. W., Rudnev, A., Tikhomirov, A., Ozhogin, V. I.
• Format: Journal Article
• Language: English
• Published: 18-04-1994
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.111703

We report a novel approach for obtaining precise control of both p- and n-type dopant concentrations in bulk Ge single crystals. High-purity Ge single crystals of controlled 74Ge/70Ge isotope composition ratios were grown and subsequently doped by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios were precisely determined by the thermal neutron fluence and the [74Ge]/[70Ge] ratios of the starting Ge materials, respectively. Application of NTD to seven crystals with 0≤[74Ge]/[70Ge]≤4.34 lead to p-type Ge:Ga,As with compensation ratios in the range 0–0.76. The ability to grow crystals with accurately controlled Ge isotope mixtures allows us to obtain ratios anywhere between 0 and 1 for both p- and n-type doping.