Characterization of tellurium and silicon as n-type dopants for GaAsBi

Abstract

Films of n-GaAs1-xBix films were grown via molecular beam epitaxy using both Si and Te as dopant sources. Electron mobility was characterized by Hall effect measurements as a function of carrier concentration and Bi content for films with bismuth fractions of x = 0.02 and x = 0.06. While GaAsBi:Te shows lower majority carrier mobility than GaAsBi:Si at low Bi concentrations, the two become comparable as Bi content increases. Furthermore, it was observed that in the presence of bi-metallic Bi-Ga droplets on the film surface, films doped with Si display p-type behavior, likely due to Si preferentially occupying group-V sites. The use of Te as a dopant always resulted in n-type epilayers, making it a more reliable dopant choice for high Bi content films. Finally, ex situ annealing was studied as a method to improve majority carrier mobility in GaAs0.98Bi0.02:Te films, with a 10 min anneal at 350 °C resulting in a 30% improvement in electron mobility. Improvement of film quality was confirmed through spectroscopic ellipsometry examination of film optical properties. Annealing at higher temperatures resulted in electrical, optical, and structural degradation of the GaAsBi films.

Performance assessment of a triple-junction solar cell with 1.0 eV GaAsBi absorber

“…Studies have shown that an intrinsic 1.0 eV GaAsBi (~ 5.5% Bi) is slightly p -type with a carrier density of 1 × 10 15 –1 × 10 16 cm −3 [ 32 ]. Although it is possible to dope GaAsBi either p - or n -type, which could potentially improve the subcell’s V oc , there is a risk that already low carrier lifetimes in the bismide will decrease even further [ 26 , 33 ]. To stay on the safe side, we used an intrinsic GaAsBi.…”

Investigation of the effect of substrate orientation on the structural, electrical and optical properties of n-type GaAs1−xBix layers grown by Molecular Beam Epitaxy

“…For electrical characterization of these devices, all samples have been fabricated in form of circular mesas. Ge/Au/Ni/Au Ohmic contacts were thermally evaporated on the back side of the wafer, with thickness (10,20,20 and 150) nm, respectively. Then rapid thermal annealing (RTA) in an Ar atmosphere was performed at 380℃ for 30 seconds.…”

“…(100) GaAs(1−x)Bix [7,10,11,[17][18][19][20]. Therefore, it is worth noting that the structural and optical properties of n-type GaAs(1−x)Bix alloys and devices using non-(100) GaAs substrates have not been investigated yet.…”

Structural and optical properties of n-type and p-type GaAs(1−x)Bi x thin films grown by molecular beam epitaxy on (311)B GaAs substrates

“…As pointed previously, there are few studies on optical and electrical properties of nand p-doped GaAs(1−x)Bix alloys [14][15][16][17][18][19][20][21]. Particularly, it was shown that the incorporation of Bi suppresses the formation of GaAs-like electron traps, thus reducing the total trap concentration in dilute GaAs(1−x)Bix layers as compared to GaAs grown under the same growth conditions [18].…”

“…Remarkably, it has been shown that enhancement of Bi incorporation in GaAs (1−x) Bi x thin films could be obtained by using (311)B orientation [9]. On the other hand, while optoelectronic devices require a controllable methodology for the doping of alloys, there are relatively a very few studies addressing the doping process of only (100) GaAs (1−x) Bi x [14][15][16][17][18][19][20][21]. These investigations have particularly concentrated on the effects the doping has on the structural, electrical and optical properties.…”