Growth optimization of InAs/GaAs quantum dots and performance enhancement of a GaAs tunnel diode by embedding quantum dots for solar cell application

Abstract

We report the performance enhancement of a molecular beam epitaxy grown GaAs tunnel diode embedded with InAs quantum dots (QDs) for tandem solar cell application, and characterization of tunnel diodes embedded with InAs QDs grown with different growth parameters. Prior to the growth and fabrication of the tunnel diode, InAs QDs were grown under different growth durations and temperatures. The InAs QD samples grown in a temperature range from 480 to 520 °C for a duration of 32 s showed the highest areal fill fraction by InAs QDs. Tunnel diodes embedded with InAs QDs that were grown at various growth conditions were fabricated and characterized. We found that the tunnel diode embedded with InAs QD grown at 520 °C showed the highest peak tunnel current density among all the samples. The enhanced performance of the InAs QD embedded tunnel diode is attributed to the large areal fill fraction produced by the presence of large InAs QDs having high density, which are formed at sufficiently high growth temperature and long growth duration.

Deep levels in metamorphic InAs/InGaAs quantum dot structures with different composition of the embedding layers

“…Since the end of the last century, In(Ga)As nanostructures embedded into an A 3 B 5 matrix are actively used as highefficient structures for optoelectronic devices [1]. Primarily well-studied GaAs was used as a base matrix material, and a significant success has been achieved in engineering of both light sensors and highly-efficient light-emitting devices [2][3][4][5][6][7][8][9]. In the last decade, many researches aimed to change the widegap GaAs buffer to a InGaAs metamorphic buffer (MB) to go deeper in the infrared [10][11][12].…”

Detailed analysis and performance limiting mechanism of Si delta-doped GaAs tunnel diode grown by MBE

“…However, growing such TDs as-designed is difficult due to practical limits of the dopants. [17][18][19] Fortunately, sufficiently high hole concentrations (10 19 -10 20 cm −3 ) with low dopant diffusion across neighboring layers and good surface morphology can be obtained by Be-doped p-GaAs that is grown by the low-temperature molecular beam epitaxy (MBE) technique. 20) Meanwhile, the highest achievable electron concentrations in Si-doped n-GaAs are only 10 18 -10 19 cm −3 .…”