Search

Indium (In) inclusions have been found in 〈100〉 indium phosphide (InP) single crystals grown in In-rich melt by the liquid-encapsulated Czochralski (LEC) method. Two kinds of In inclusions with different morphologies, one is lath-like and the other is polyhedral, have been observed. Most of the In inclusions are lath-like and their long sides are always parallel to the $$[0\overline{1}1]$$ or $$[0{\overline{1}}{\overline{1}}]$$ orientation. In (100) InP wafers, these inclusions mainly distribute in two regions viz., center of the wafer and annular belt at a certain distance from the center. These special distributions of In inclusions in InP crystals were found in our experiments for the first time. In order to clarify the cause of the special distributions of In inclusions, numerical simulations have been carried out on the melt convection in the process of InP crystal growth. The results show that the rotations of crystal and crucible significantly affect the number and direction of convection cells in the melt, which have a great influence on the enrichment and distribution of excess In at the solid–liquid interface. Different melt convections modify the radial distributions of excess In atoms near the solid–liquid interface and result in different radial distributions of In inclusions in the crystals.

Positron lifetime measurements have been carried out on liquid-encapsulated Czochralski-grown undoped InP samples sliced from the middle part of ingots over the temperature range 10–300 K. And at 70 K, the spectra have been measured in darkness, under illumination of infrared LED, and with illumination off is one sample. The measurements at low temperature reveal different concentration of hydrogen indium vacancy complex VInH4 in these samples. A relatively higher concentration of VInH4 in samples grown from P-rich undoped InP melts can be shown. The increase of resistivity of these samples can be speculated when temperature is low enough.

Semi-insulating (SI) InP wafers of 2 and 3 in. diameters have been prepared by annealing undoped LEC InP at 930 degreesC for 80 h under pure phosphorus ambient (PP) and iron phosphide ambient (IP). The electrical uniformity of annealed undoped SI wafers, along with a Fe-doped as-grown SI LEC InP wafer, has been characterized by whole wafer PL mapping and radial Hall measurements. Defects in these wafers have been detected by photo-induced current transient spectroscopy (PICTS). The results indicated that the uniformity of IP wafer is much better than that of PP wafer and as-grown Fe-doped Si InP wafer. There are fewer traps in undoped SI InP IP wafer than in as grown Fe-doped and undoped SI InP PP wafer, as evidenced by PICTS. The good uniformity of the IP wafer is related to the nonexistence of high concentration of thermally induced defects. The mechanism for this phenomenon is discussed based on the results. (C) 2002 Elsevier Science B.V. All rights reserved.

A large quantity of high purity InP crystal material has been produced by the phosphorus in-situ injection synthesis. In the injection method, phosphorus reacts with indium very quickly so that the rapid polycrystalline synthesis is possible. The injection speed, melt temperature, phosphorus excess, and so on are also important for a successful synthesis process. About 3200-4800 g stoichiometric high purity poly InP is synthesized reproducibly by improved P-injection method in the high-pressure puller. Twin-Free InP single crystals with diameter of 50-110 mm can be pulled after the synthesis. In the present work, the characterization of InP polycrystalline was studied by van der Pauw method, GDMS, and PL.

P-rich of InP crystals are rather difficult to achieve, due to the high phosphorus pressure at the melting point. By using the P-injection in-situ synthesis method, there is excessive phosphorus in the melt. In the conditions of M/sub In/ [In]/sub mol/, the melt might be P-rich. Since a high thermal stress exists in the LEC growth process with large temperature gradient, it is difficult to release stress, a large number of dislocations come into being around the pores. The pores are distributed in the ingots irregularly. The diameter of the pores is from

Sn-doped InP is being used as a platform for a wide variety of fiber communications components, including lasers, LEDs, semiconductor optical amplifiers, modulators and photo-detectors. The more the diameter is, the more imperfection of the InP crystal would be. The substrates with large diameter are desired in order to realize low devices cost. In recent years, we have developed a high quality 3-inch and 4-inch Sn-doped InP single crystal growth using the HP-LEC method after P-injection direct synthesis polycrystalline. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystalline, three inch and four inch twin-free Sn-doped InP crystals can be obtained even with a shoulder angle of up to 35/spl deg/-90/spl deg/, and defects caused by thermal decomposition appear on the surface of the crystals during pulling. For LEC InP crystals, twin formation can be effectively suppressed by optimization of growth conditions, such as thermal field, doping concentration, etc. However, it is difficult to grow twin-free LEC InP in a similar way. It is observed that the yield of single crystal InP can be increased by controlling the ingot shape of a gradually increased diameter.

Semi-Insulating InP is used in microelectronics devices and integrated opto-electronic circuits. The Chinese InP research team used a direct P-injection synthesis and LEC crystal growth method to prepare polycrystalline InP and to grow the undoped InP and Fe-doped SI-InP single crystal in the same puller. We can get very low concentration silicon in the ingots by using this method. And in the InP crystal the main impurity is silicon, which acts as a shallow donor in the crystal. The undoped InP has been found to be annealed into SI material around 900/spl deg/C. The Chinese InP research team present a model to explain the possible mechanisms of the Semi-Insulating behavior of bulk InP material. The physical properties of SI-InP have been studied. We have combined a variety of techniques such as FT-IR, PICTS, Hall, TDH, PL, PAS, and GDMS to investigate SI-InP. Most of the data can be explained by this model. Furthermore we compared the results of the MOCVD material, which grow on the annealed undoped SI-InP and on Fe-doped SI-InP.

High purity InP is necessary for the preparation of high quality InP single crystal especially low Fe content semi-insulating and annealed undoped semi-insulating InP single crystal. In-situ phosphorus injection synthesis of InP has several advantages over the two-step process of compounding and growing in separate furnace. In 1982 it was reported by our group that around 500g InP was synthesized and semi-insulating InP single crystals grown in one step in 30-60 minutes. A large high pressure puller have been set up, which can be used to synthesize and grow large diameter InP single crystal in our laboratory. Now 3400g InP can be synthesized reproducible and single crystals can be grown in the puller. The red phosphorus used for synthesis is contained in two vessels, which can be manipulated separately during the synthesis process. The two phosphorus vessels are heated by the auxiliary heater and the phosphorus vapour is injected into the indium melt in the crucible. We have developed a process for the rapid synthesis of InP. The whole synthesis process only needs 60-70 minutes. The synthesized InP could be indium-rich, stoichiometric or phosphorus-rich which depend on the quantity of excess phosphorus and other conditions such as the temperature of indium melt in the crucible, the thermal field, phosphorus injection speed etc. After the synthesis, InP crystal can be pulled by the conventional LEC method. Twin-free 3-inch and 4-inch InP single crystal can be obtained. The InP single crystal wafer is cut from the ingot for the measurement of electronic parameters. The carrier concentration of P-injection in-situ synthesis InP at T = 300 K is n = 2 /spl times/ 10/sup 15/ - 10/sup 16/ cm/sup -3/, the mobility is 3500 4900 cm/sup 2//Vs. These depend on the raw materials used. At T = 77 K the best result n = 2.36 /spl times/ 10/sup 15/ cm/sup -3/, the mobility is 4.8 /spl times/ 10/sup 4/ cm/sup 2//Vs. This kind of InP can be made semi-insulating with high temperature annealing or low iron doping levels.

A large quantity of high purity InP crystal material has been produced by the phosphorus in-situ injection synthesis and liquid encapsulated Czochralski (LEC) growth process. The in-situ process exhibits several advantages over the two-step process of compounding and growing in separate furnaces. About 2500-5000g stoichiometric poly InP is synthesized reproducibly by P-injection method in the high-pressure puller. Twin-f ree InP single crystals with diameter of 60-100 mm can be pulled after the synthesis.

Undoped liquid encapsulated Czochralski (LEC) InP samples have been studied by Hall effect, glow discharge mass spectroscopy (GDMS) and infrared absorption spectroscopy. A systematic discrepancy has been found between the Hall electron concentration and net donor concentration measured by GDMS. The electron concentration is always higher than the net shallow donor concentration by about (3-6)/spl times/10/sup 15/ cm/sup -3/. A hydrogen indium vacancy complex donor defect V/sub In/H/sub 4/ was detected regularly by infrared absorption spectroscopy in all undoped LEC InP samples. The fact can be explained by taking into account the existence of the donor defect in as-grown undoped LEC-InP.