Temperature-Dependent Operation of GaAs Quantum Nanodisk LEDs with Asymmetric AlGaAs Barriers

Quantum dot photonic devices such as light-emitting diodes (LEDs), laser diodes (LDs), high-speed modulators, and semiconductor optical amplifiers are attractive because of their small threshold voltages, low power consumption, and temperature stability. We have studied and developed a defect-less top-down dry fabrication process for GaAs quantum nanodisk (QND) LEDs with diameters of less than 20 nm and thicknesses of 8 nm by employing a bionanotemplate, neutral beam etching, and asymmetric AlGaAs/GaAs regrowth via metalorganic vapor phase epitaxy. Al
_x
Ga
_1-x
As barriers with high (Al
_0.3
Ga
_0.7
As) and low (Al
_0.17
Ga
_0.83
As) aluminum contents were used between QNDs in the in-plane and vertical directions, respectively. This permits the control of the deep band energy offset between GaAs QNDs and Al
_x
Ga
_1-x
As barriers, leading to stable room-temperature operation. The temperature dependence of the optical properties of the QND LED was measured by electroluminescence, and we found that the energies and their transient behaviors were strongly affected by the band offset energies between the QNDs and the aluminum-rich barriers. Therefore, we could enhance the optical performances of our symmetric QND LED with low-Al-content barriers by developing asymmetric Al
_x
Ga
_1-x
As barriers with low-Al-content vertical barriers and high-Al-content in-plane barriers.