Vacancy-donor complexes in highly n-type Ge doped with As, P and Sb

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Understanding defects in doped semiconductors is crucial for electronic device performance.
• Germanium (Ge) is a key semiconductor material with applications in various electronic and optoelectronic devices.
• Dopant atoms like Arsenic (As), Phosphorus (P), and Antimony (Sb) introduce point defects in Ge.

Purpose of the Study:

• To investigate the nature and concentration of defects in Ge doped with As, P, and Sb using positron annihilation spectroscopy.
• To correlate experimental findings with theoretical electronic structure calculations.
• To elucidate the role of dopant type and concentration on defect formation and positron trapping.

Main Methods:

• Positron annihilation spectroscopy (PAS), including Doppler broadening and positron lifetime measurements.
• Experimental techniques were complemented by ab initio electronic structure calculations.
• Controlled doping of Ge with As, P, and Sb to a concentration of ~10^19 cm^-3.

Main Results:

• Positron lifetime measurements indicate that the open volume of defect centers does not exceed that of a monovacancy.
• In As-doped Ge, a complex of a vacancy with at least three As atoms is the dominant trap at room temperature.
• In P-doped Ge, two competing defect complexes were observed, with vacancy-P complexes dominating at room temperature and less-P complexes at low temperatures.
• In Sb-doped Ge, multiple trap types compete for positron trapping across all measured temperatures.

Conclusions:

• The study characterizes specific vacancy-dopant complexes in Ge, providing insights into defect behavior.
• The findings highlight the influence of different dopants (As, P, Sb) on defect structures and their impact on positron trapping dynamics.
• The research contributes to a fundamental understanding of defect engineering in semiconductors for tailored electronic properties.