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I.G.V. acknowledges the support of project VIGNETRANSFER (grant number PDC2022-133445-I00) and I.R.S. acknowledges the support of project TEIDE (grant number TED2021-131990B-I00), both funded by the Spanish Ministerio de Ciencia e Innovacion/Agencia Estatal de Investigacion [MCIN/AEI DOI: 10. 13039/501100011033]. The epitaxy runs reported in this paper were carried out in an MOVPE reactor retrofitted with project RENOAIX200 (grant number EQC2019-005701-P) funded also by Spanish MCIN/AEI and FEDER "Una manera de hacer Europa". Part of the equipment used in this research for TPV cell manufacturing was acquired through project LABCELL30 [grant number EQC2021-006851-P] with funding from the Spanish Ministerio de Ciencia e Innovacion/Agencia Estatal de Investigacion [MCIN/AEI 10.13039/501100011033] and the European Union "NextGenerataionEU"/PRTR ''. V. Orejuela is funded by the Spanish Ministerio de Ciencia e Innovacion (MCIN) through an FPI grant (PRE2019-088437).

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Arsenic Diffusion in MOVPE-Grown GaAs/Ge Epitaxial Structures

Publicat a:Advanced Electronic Materials. 10 (9): - 2024-09-01 10(9), DOI: 10.1002/aelm.202400021

Autors: Orejuela, V; Rey-Stolle, I; García, I; García-Tabares, E

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Germanium is reemerging as a prominent material in the semiconductor field, particularly for electronic applications, photonics, photovoltaics, and thermophotovoltaics. Its combination with III-V compound semiconductors through epitaxial growth by metal-organic vapor phase epitaxy (MOVPE) is instrumental and thus, the comprehension of the sequential stages in such epitaxial processes is of great importance. During the deposition of GaAs on p-type Ge, the formation of n/p junctions occurs when As diffuses into Ge. It is found that this formation begins in the so-called AsH3 preexposure where Ge substrate is first exposed to AsH3. Also important is the fact that both free carrier profiles and As profiles indicate that prolonged AsH3 preexposure times lead to deeper diffusion depths for the same process time. This effect is concomitant with the degradation of the Ge surface morphology, characterized by higher roughness as the AsH3 preexposure duration is extended. Unlike ion-implanted As in Ge, which shows a quadratic dependent diffusivity, this MOVPE investigation using AsH3 indicates a linear relationship, consistent with Takenaka et al.'s MOVPE study using TBAs. The analysis of As profiles alongside simulations, with and without subsequent GaAs epitaxy, suggests the generation of Ge vacancies during the process, contributing to deeper As diffusion.

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