Annealing behaviour of high-dose-implanted nitrogen in InP

Concentration profiles of nitrogen in vacuumannealed pand n-type single-crystal (1 0 0) InP implanted with 1]101630 keV 15N` ions cm~2 have been studied by Secondary Ion Mass Spectrometry (SIMS) and Nuclear Resonance Broadening (NRB) techniques. Damage induced by the nitrogen implantation was studied by Rutherford Backscattering Spectrometry (RBS) and channeling. Annealing the samples led to loss and redistribution of nitrogen in the temperature range from 575 to 675 °C. At temperatures from 575 to 600 °C, rapid migration of nitrogen towards the sample surface was observed. The n-type InP material had a very dominant tendency for surface nitrogen build-up, whereas the p-type material had a markedly smaller surface peak in the nitrogen distribution. The surface peak in n-type material is due to sulphur acting partly as a diffusion barrier. SIMS analyses showed sulphur build-up on the surface in the course of annealing. At temperatures from 600 to 675 °C, the nitrogen profiles of nand p-type InP were similar. A small loss of nitrogen was observed at 625—675 °C. Two different recovery stages were observed at 575—600 °C and at 625—650 °C. The corresponding activation energies for nitrogen loss are 2.9 and 3.0 eV, respectively. PACS: 61.72.Vv; 61.72.Cc; 66.30.Jt The use of III—V compound semiconductors for the fabrication of various electronic and optoelectronic devices has received growing interest in the last years. In planar technology, doping of these materials by ion implantation is of considerable importance for introducing electrically active or isolating regions [1]. The damage accompanying ion implantation may, however, be detrimental to device performance and has to be removed or controlled by suitable annealing techniques. Various aspects of nitrogen implantation into InP have earlier been studied in the literature. Most of the published data on implantation of InP have concentrated . on investigation of the effects of various implantation parameters and damage production [2—4], and on measurements of electrical properties [5—7]. Implantation of nitrogen has been used to create high-resistivity layers in InP using a method called Formation Of Insulating Layers by Ion Implantation (FOILIM) [8]. This technique has received much attention because it is possible to create a Semiconductor-On-Insulator (SOI) structure to be used as a substrate for further device fabrication. In FOILIM technique, MeV nitrogen ions with doses from 5]1014 to 1016 cm~2 have typically been used for the formation of high resistivity layers in InP [8]. Nitrogen ion implantation into InP has several advantages compared to light ion bombardment. Xiong et al. [8] have shown that the nitrogen-implantation-induced high resistivity layer has better thermal stability. In addition to this, the heavier nitrogen ions have smaller energy straggling and smaller lateral spreading under a shadow mask during device fabrication. During MeV-ion implantation, electronic damage is generated in the near surface region due to electronic stopping. Nuclear stopping instead creates structural damage in the region near the end of the ion range. The energy of nitrogen ions defines a maximum depth of the buried layer. After implantation, the generation of the high-resistivity layer requires thermal annealing in order to remove radiation-induced damage. During high temperature annealing, the damaged layer may undergo phase transition which can lead to redistribution of implanted nitrogen and resistivity changes. Thus, the thermal stability of resistivity changes is of importance. In addition to buried insulating layers, midgap compensating levels can be obtained in III—V compound semiconductors by nitrogen implantation [1]. The kind and concentration of defects produced during ion implantation in various III—V compound semiconductors have been recently studied extensively by Wesch et al. [9]. It is known that conditions for annealing are influenced by the type and concentration of defects. The purpose of this work was to study the annealing behaviour of pand n-type InP implanted with keV energy nitrogen ions to produce shallow layers with strong