Subnano-scale selective etching and nano-scale pore array formation on inp [001] surfaces by a wet electrochemical process

Hamamatsu, A.; Kaneshiro, C.; Sato, Taketomo; Fujikura, Hajime; Hasegawa, Hajime

doi:10.1109/iciprm.1999.773743

Cited by 1 publication

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“…This surface exhibited a porous structure involving oxide components. Further study revealed that a porous (100) InP structure similar to that reported for the (111) InP surface [6][7][8][9] is formed in this passive region of the overpotential as discussed elsewhere 12) . XPS studies were also carried out on the anodically processed surfaces of n-InP in order to further confirm the presence of active-passive transition.…”

Section: Surface Morphology and Xps Studymentioning

confidence: 75%

Electrochemical Etching of Indium Phosphide Surfaces Studied by Voltammetry and Scanned Probe Microscopes

Kaneshiro¹,

Sato²,

Hasegawa³

1999

Jpn. J. Appl. Phys.

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Using voltammetry, X-ray photoemission spectroscopy (XPS), in situ electrochemical scanning tunneling microscopy (STM), ex situ atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements, electrochemical etching modes for n-InP surfaces were investigated and optimized for uniform and controlled etching in an HCl electrolyte. The voltammograms indicated the presence of active and passive regions. The surfaces obtained in the active region were clean and featureless with an rms roughness of 1.8 nm. On the other hand, the oxide covered surfaces obtained in the passive region were nonuniform and porous. Etching characteristics of the d.c. photo-anodic mode and the pulsed avalanche mode were then investigated and compared. Both modes were found to be highly controllable and produced uniform and clean surfaces, consuming eight holes per molecule of InP. In particular, the pulsed avalanche etching mode realized an extremely high etch rate of 3x10 -5 nm/pulse.KEYWORD: InP, etching, electrochemical process, voltammetry, scanned probe microscope IntroductionScaling down of device feature size to the nanometer order is a recent general trend, not only for Si devices, but also for III-V devices. Thus, the etching process, the spatial uniformity and the precise controllability of the etching depth along with minimal process-induced damages have become increasingly important. Owing to its low damage nature, wet etching in various acid solutions 1) is widely used in various steps of InP and related material fabrication. However, precise control of the etching depth is extremely difficult in wet etching, because the etch rate is very sensitive to the temperature and the local fluctuation of the etchant composition.On the other hand, electrochemical etching appears to be promising for achieving high controllability, since the anodic reaction can be precisely controlled by the amount of charge according to Faraday's law of electrolysis. However, it is not clear at present whether it is possible to perform uniform and controlled etching of n-InP by the electrochemical reactions on InP surfaces in the electrolyte. In the literature, only limited works 2-5) have been reported on the anodic etching of InP, and their etch rate and uniformity have not been clarified. More recent anodization experiments 6-9) on InP using HCl electrolyte have led to the formation of InP porous structures. Although such an anodization mode is interesting for the formation of quantum structures and photonic crystals, it is not suitable for uniform etching. On the other hand, it has also been recently shown by our group that electrochemical etching applied just before electrodeposition is effective for the realization of well-behaved Schottky diodes with oxide-free, stress-free and pinning free interfaces for InP 10) . Similar results have been reported for n-GaAs Schottky contacts 11) . However, the mechanism, the etch uniformity and the etch rate of such a predeposition etching process have not been clarified yet.The purpose...

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