RESUMEN
Photo-atomic layer etching (photo-ALE) of GaAs and AlGaAs semiconductors was investigated in deionized H2O and aqueous solution of NH4OH under weak excitation conditions ( P ≈ 20 mW/cm2). The process is based on digital photocorrosion in a processed solution and a negligible corrosion during the light-off phase employed for dissolution of the photocorrosion products. An inductively coupled plasma mass spectroscopy (ICP-MS) analysis revealed that photo-ALE of GaAs in an aqueous solution of NH4OH proceeds linearly with the number of reaction cycles, typically at â¼0.1 nm/cycle, and with the light-off phase as short as 22 s sufficient to entirely dissolve the photocorrosion products generated during a 3 s irradiation. In agreement with the ICP-MS data, the constant photo-ALE rates in NH4OH were also demonstrated in situ with the photoluminescence measurements. Our results suggest that the congruent decomposition of III-V materials and the etching of deep structures with atomic layer resolution could be facilitated by switching in situ between different etching environments.
RESUMEN
Photocorrosion of semiconductors is strongly sensitive to the presence of surface states, and it could be influenced by electrically charged molecules immobilized near the semiconductor/electrolyte interface. The underlying mechanism is related to band bending of the semiconductor structure near the surface and the associated distribution of excited electrons and holes. The authors have employed photoluminescence of GaAs/AlGaAs quantum heterostructures for monitoring in situ the photocorrosion effect, and demonstrating detection of nongrowing Legionella pneumophila suspended in phosphate buffered saline solution. Antibody functionalized samples allowed direct detection of these bacteria at 10(4) bacteria/ml. The authors discuss the sensitivity of the process related to the ability of creating conditions suitable for photocorrosion proceeding at extremely slow rates and the interaction of an electric charge of bacteria with the surface of a biofunctionalized semiconductor.