Deep etching of GaP was performed by high-density plasma using an inductively coupled plasma (ICP) etcher. The effects of process parameters such as the gas combination (Cl-2/N-2), chamber pressure, inductive power and rf chuck power were investigated. The dependences of the etch rates and selectivity on the rf chunk power and chamber pressure were studied using the response Surface method. The results obtained can be further interpreted by the plasma properties (ion flux and de bias) measured in situ by a Langmuir probe. With an increase in the chamber pressure to 4 Pa, a maximum etch rate of similar to7.5 mum/min for GaP can be obtained under a Cl-2/(Cl-2 + N-2) gas mixture of 0.8, ICP power of 800 W, and rf power of 100 W The increase in the etch rate with an increase in chamber pressure indicates that reactive radicals are the main etching species. To clarify the etching mechanism, the surface reaction of GaP under various Cl-2/(Cl-2 + N-2) gas mixtures was investigated by x-ray photoelectron spectroscopy and atomic force microscopy. In addition, quantitative analysis of the plasma-induced damage was attempted in order to discuss the mechanism of leakage current density and brightness with various rf powers on AlGaInP light-emitting diodes with a thick GaP window layer. Under a fixed ICP power applied, it is found that the duration of the plasma (not dc bias voltage) has a major effect on leakage current performance. Finally, an effective recovery method is developed, in which plasma-induced damage can be recovered in a boiling NaOH solution with the range of our experiments.