Uniformity and physical properties of semi-insulating Fe-doped InP after wafer or ingot annealing

Abstract

Semi-insulating Fe-doped InP was annealed under different conditions and investigated by Hall effect, extrinsic photocurrent mapping, chemical etching, and optical microscopy. The resistivity is increased for any treatment, particularly in wafer-annealed InP. This result is probably due to strong losses of shallow donors. Remarkable differences exist between the structural properties of the wafer and ingot annealed material; wafer annealing produces a quick elimination of growth striations and decoration microdefects while ingot-annealed InP still retain these microdefects, both along dislocations and in the matrix. The photocurrent maps indicate that the thermal treatments normally improve the doping uniformity (especially the short-range fluctuations). The best uniformity is achieved for the long annealing time (⩾50 h), while a slow cooling rate improves the mobility.

Microdefects and electrical uniformity of InP annealed in phosphorus and iron phosphide ambiances

“…In recent years, heat treatment of InP has been studied in order to produce SI material with a low Fe concentration [7][8][9][10][11] and improve the electrical uniformity of Fe-doped SI InP [5,12,13]. Annealing of undoped InP wafer in an iron phosphide ambiance has proved to be a promising method for the preparation of SI material with good uniformity [8,9,11].…”

Uniformity of semi-insulating InP wafers obtained by Fe diffusion

“…2,3 Thermal treatments at about 900°C carried out on wafers have proved to be effective for improving the material homogeneity: striations are readily eliminated and microdefects can be dissolved while the electrical characteristics are generally improved. 4 On the other hand, postgrowth ingot annealing was found to be much less effective since the final resistivity exhibited marked gradients across the crystal diameter and around crystal defects. 4,5 Recently, alternative approaches to the preparation of SI InP were presented.…”

“…4 On the other hand, postgrowth ingot annealing was found to be much less effective since the final resistivity exhibited marked gradients across the crystal diameter and around crystal defects. 4,5 Recently, alternative approaches to the preparation of SI InP were presented. For instance, it was reported that the annealing of undoped InP in a closed ampoule containing elemental Fe and red P results in material with low Fe content but high resistivity and good uniformity.…”

Semi-insulating InP wafers obtained by Fe-diffusion

“…The existence of wafer areas having at the same time high resistivity and high PL intensity is surprising as it is well known that generally the intrinsic PL intensity is inversely proponional to the electrically active ([Fe"]+[Fe"]) concentration [ 1 I] [12]. In references [4,5] it was shown that the shallow donors (believed to be hydrogenrelated complexes [ 131) are annihilated by the thermal processes. The way they annihilate is probably via outdiffusion of hydrogen.…”

“…Thermal treatments at about 900 "C, carried out on wafers, have proved to be affective in order to improve the material homogeneity: striations are readily eliminated and microdefects can be dissolved while the electrical characteristics arc generally improved. Post-growth ingot annealing was found to be less effective as the final resistivity exhibited pronounced gradients along the crystal diameter [4,5]. Alternative approaches to the preparation of SI InP were attempted, like for instance the annealing of undopcd TnP wafcrs in a close ampoule containing elemental Fe and red P. The resulting material exhibited a Fe content tower than traditionai as-grown SI InP but at the same time high resistivity and good uniformity [6,7J. In this paper we shall present a process for the production of SI InP wafers which includes: i) dcposition of very thin Fe layers on both surfaces of as-cut 2" wafers , ii) high temperature annealing, iii) double-sidc lapping and polishing.…”