M. Uchida

Fe Doping and Preparation of Semi-Insulating InP by Wafer Annealing under Fe Phosphide Vapor Pressure.

Semi-insulating (SI) InP has been industrially produced by doping Fe atoms as deep acceptors. Fe concentrations in InP are, however, largely varied from top to tail along the crystal growth axis due to impurity segregation. In the present work, we have examined the possibility of vapor-phase Fe doping for fabrication of 50- and 75-mm-diameter SI InP wafers with constant Fe concentrations using a wafer annealing procedure. A small amount of Fe was charged with red phosphorus in ampoules in which InP wafers were annealed. It was found that the vapor-phase doping is effective for Fe doping of InP. The present technology can be applied for the fabrication of low Fe-doped SI InP wafers with similar Fe concentrations of all wafers from one InP ingot.

Semi-insulating InP through wafer annealing

Recent investigations in various affiliations opened a possibility for preparation of semi-insulating (SI) InP with extremely low Fe concentrations through wafer annealing procedures. In this paper, these investigations are reviewed including the latest data on 75 mm diameter SI InP, and possible mechanisms of the SI behavior after wafer annealing are discussed.

Reproducibility in the fabrication of undoped semi-insulating InP

Various annealing conditions for realizing the fabrication of undoped semi-insulating (SI) InP has been systematically studied in our laboratory for several years. In the present paper, these results are reported. It was found that by annealing at 950/spl deg/C for 40 hrs under the phosphorus vapor pressure of 1 atm, the reproducible preparation of undoped SI InP can be achieved with the maximum number of 30 two-inch diameter wafers per batch. It was also found that a multiple-step wafer annealing (MWA) is very effective in improving the uniformity of electrical properties.

Fe doping and preparation of semi insulating InP by wafer annealing under Fe phosphide vapor pressure

Semi-insulating (SI) InP has been industrially produced by doping Fe atoms as deep acceptors. Fe concentrations in InP are, however, largely varied from top to tail along the crystal growth axis because of impurity segregation. In the present work, we have examined the possibility of vapor phase doping for producing 50 mm diameter SI InP wafers with constant Fe concentrations by using a wafer annealing procedure. Small amount of Fe was charged with red phosphorus in ampoules in which InP wafers were annealed. It was found that the vapor phase doping is effective for Fe doping in InP. The present technology can be applied for the production of low Fe doped SI InP wafers with the same Fe concentration for all wafers from one InP ingot.

Photoelastic characterization of residual strain in MWA SI InP crystal wafers

Residual strain in semi-insulating InP wafers was characterized by using a scanning infrared polariscope (SIRP). SIRP maps of single-step and multi-step annealed wafers are compared with those of the as-grown state. In general, a fair decrease of residual strain by wafer annealing was found. The most homogeneous distribution was revealed in the wafer treated by multiple wafer annealing.

Semi-insulating InP crystal wafers characterized by different nondestructive techniques

Nondestructive techniques of mapping of residual strain, photoluminescence and resistivity were utilized to optimize the multiple wafer annealing (MWA) procedure of undoped or slightly Fe doped InP crystal wafers under phosphorous atmosphere. The annealing procedure optimized did not additionally produce unwanted residual strain but reduced and homogenized it. In conclusion, MWA has proved to be a promising method to obtain semi-insulating InP crystals without undesired high Fe doping.

VGF crystal growth and vapor-phase Fe doping technologies for semi-insulating 100 mm diameter InP substrates

100 mm diameter <100> semi-insulating InP substrates were obtained after conductive undoped wafers were annealed under volatile FeP/sub 2/ atmosphere. Undoped crystals were grown by the VGF method using a high pressure furnace. In this growth method, we investigated the reduction of the temperature fluctuation by computer simulation for preventing twinning. The temperature fluctuation near the seed crystal could be reduced from /spl plusmn/0.3/spl deg/C to /spl plusmn/0.03/spl deg/C after improvement of the hot-zone, based on the simulation results. Semi-insulating InP is conventionally produced by Fe doping during crystal growth. In the conventional doping method, the Fe concentration is varied along the growth axis due to Fe segregation in InP. In order to obtain good homogeneity of Fe concentrations from wafer to wafer, we have developed a new Fe doping technology in which wafers are annealed under volatile FeP/sub 2/ atmosphere. In this work, we applied this Fe doping technology to 100 mm diameter <100> InP substrates and could obtain large diameter semi-insulating substrates.