Towards higher electron mobility in modulation doped GaAs/AlGaAs core shell nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Precise control of semiconductor nanowire conductivity is vital for electronic and optoelectronic devices.
• Understanding doping mechanisms and their impact on electron mobility and radiative efficiency in nanowires is essential.

Purpose of the Study:

• Investigate the electronic properties of n-type modulation-doped GaAs/AlGaAs nanowires.
• Determine the ionization energy of Si donors in the AlGaAs shell.
• Elucidate the temperature dependence of electron mobility, photoconductivity lifetime, and radiative efficiency.

Main Methods:

• Optical pump-terahertz (THz) probe spectroscopy.
• Photoluminescence spectroscopy.
• Temperature-dependent measurements from 5 K to 300 K.

Main Results:

• Determined a Si donor ionization energy of 6.7 ± 0.5 meV at 52 K.
• Observed excellent electron mobility (4360 ± 380 cm²/Vs at 5 K) limited by interface scattering below the ionization temperature.
• Identified polar scattering via longitudinal optical phonons as the dominant mechanism above the ionization temperature, yielding room-temperature mobility of 2220 ± 130 cm²/Vs.
• Demonstrated Si donor passivation of interfacial trap states, prolonging photoconductivity lifetimes and enhancing room-temperature radiative efficiency to over 10%.

Conclusions:

• Si donors in GaAs/AlGaAs nanowires effectively control electronic properties.
• Interface and phonon scattering mechanisms dictate electron mobility across different temperature regimes.
• Donor passivation enhances nanowire performance, paving the way for improved nanodevices.