Combination of Reactive-Ion Etching and Chemical Etching as a Method for Optimizing the Surface Relief on AlGaInN Hetero
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ICATION, TREATMENT, AND TESTING OF MATERIALS AND STRUCTURES
Combination of Reactive-Ion Etching and Chemical Etching as a Method for Optimizing the Surface Relief on AlGaInN Heterostructures L. K. Markova,*, I. P. Smirnovaa, M. V. Kukushkina, and A. S. Pavluchenkoa a Ioffe
Institute, St. Petersburg, 194021 Russia *e-mail: [email protected]
Received May 1, 2020; revised May 1, 2020; accepted May 1, 2020
Abstract—A relief on the surface of GaN previously released from the growth substrate is formed by a combined method in which reactive ion etching is used in combination with liquid etching (in KOH or hydrochloric-acid solutions). The dependence of obtained relief on the sequence of operations used is studied. It is shown that etching in a KOH solution followed by reactive ion etching provides the appearance of truncated hollow cones on the surface. In experiments, the ability of a hydrochloric-acid solution for etching exclusively GaN relief elements formed by reactive ion etching of the surface is also found. As a result, reactive ion etching of the sample followed by immersion into hydrochloric acid forms objects of cylindrical shape on its surface transforming at the base into conical or strongly distorted pyramidal structures. The appearance of this relief can be explained by the predominance of the chemical component in reactive ion etching with increasing distance from the sample surface. Further optimization of the relief parameters obtained as a result of combined etching is possible by varying the modes of operation under use. Keywords: gallium nitride, relief, reactive ion etching, liquid etching, light-emitting diode, light-emitting chip DOI: 10.1134/S1063782620100218
1. INTRODUCTION In recent years, more and more diverse devices have been created on the basis of high energy-gap GaN material. If in the beginning, it was used mainly in light-emitting chips of the blue and ultraviolet ranges applied in the production of white LEDs [1, 2] and lasers [3, 4], now much attention is also paid to investigations in the field of high-frequency and highvoltage applications [5, 6]. It is known that the high chemical resistance of the material makes difficult its etching in order to form semiconductor devices on its basis. The material is etched most efficiently in chlorine plasma or in alkaline solutions (KOH or NaOH). It is also possible to etch GaN in orthophosphoric acid (H3PO4), but its etching rate is negligible. In this case, the approaches themselves to etching of the material can be different depending on the scope of its application. When developing high-voltage and high-frequency elements (diodes and transistors), methods are needed, which provide plane-parallel etching of the material with the least number of defects, since the probability of current leakage in the devices under formation decreases in this case. For example, the authors of [7] used pulsed photoelectrochemical etching in a NaOH solution to obtain diodes with a breakdown voltage higher than 3 kV. Application of the same method in [8]
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