InGaP/GaAs shadow-mask for optoelectronic integration and MBE regrowth

• Published in: Journal of crystal growth 1998-12, Vol.195 (1), p.490-494
• Main Authors: Velling, P., Fix, W., Geißelbrecht, W., Prost, W., Döhler, G.H., Tegude, F.-J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; GaAs; InGaP; MBE; MOVPE; Nipi-structure; Optoelectronic devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Shadow-mask
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/S0022-0248(98)00696-4

The epitaxial shadow mask (ESM) MBE technique has proven to yield excellent device structures with highly selective contacts. The epitaxial mask used for the ESM-MBE technique consists of a (7–8 μm) AlGaAs-layer capped by approximately 1 μm GaAs. These layers are lithographically patterned for the desired design. Selective etchants are used to achieve the undercut in the AlGaAs-layer. After the (re)growth, these layers have to be removed completely to get access to the grown devices. We now demonstrate a new epitaxial mask design which allows the monolithic integration of ESM-MBE grown devices with devices which are still included in the shadow mask during a first epitaxy. This demands a high bi-directional selectivity of etchants, as well as an Al-free mask layer to prevent degradation problems during the processing. The lattice matched InGaP/GaAs material system (grown by LP-MOVPE) meets all these requirements (even though a thick InGaP layer has to placed on top of the mask). This is shown by a monolithically integrated version of an electro-optical n–i–p–i modulator (regrown in the mask windows) and an opto-electrical receiver, which was grown as part of the mask layers, to an all-optical smart pixel device. The receiver component, a photoconductive pinFET switch, exhibited state-of-the-art performance, e.g. a leakage current of less than 10 pA (−5 V) and a high channel conductance modulation of 10 5.