Synthesis, Grown And Characterization Of Bulk Indium Phosphide Crystal

Indium Phosphide (InP) has been indispensable to both optical and electronic devices. This paper used a direct P-injection synthesis and LEC crystal growth method to prepare high purity and various melt stoichiometry conditions polycrystalline InP and to grow high quality, large diameter InP single crystal in our homemade pullers. In this work, we have obtained the following results:(1) 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. In the injection method, phosphorus reacts with indium very quickly so that the rapid polycrystalline synthesis is possible. The quartz injector with two or multi-transfer tubes was used to improve the synthesis result. It will avoid quartz injector blast when the melt was indraft into the transfer tube. The injection speed, melt temperature, phosphorus excess, and so on are also important for a successful synthesis process. About 4000-6000g stoichiometric high purity poly InP is synthesized reproducibly by improved P-injection method in the high-pressure puller. We firstly reported these results in 16th IPRM Proceedings;Materials Science In Semiconductor Processing ; Journal of Rare Earths ; Chinese Journal of Semiconductors, IOCG-2007 Proceedings.(2) Long-length 2-inch, 3-inch, 4-inch semi-insulating InP single crystals have been grown by the HP-LEC method. The maximum total length of the 2-inch single crystal part was 190mm, the maximum total length of the 3-inch and 4-inch single crystal was 150mm. The key technologies of reducing twining were discussed in this paper. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystalline, the diameter 100-142mm twin-free InP crystals can be obtained even with a shoulder angle of up to 35°-90°, and defects caused by thermal decomposition appear on the surface of the crystals during pulling.(3) Some samples from these ingots have been characterized by Hall Effect and Fourier Transform Infrared (FT-IR) spectroscopy measurements respectively. The Hall Effect and FT-IR spectroscopy measurement results indicate that the carrier concentration of P-rich undoped InP is higher than that of In-rich and stoichiometric undoped InP materials. The intensive absorption peaks indicate that our phosphorus in-situ injection synthesis LEC undoped InP materials have relatively high concentration of hydrogen related complexes. It has been proved to be acting as a shallow donor in InP material by theory calculation. Generally, high concentration indium vacancy should enhance the formation of higher concentration of VInH4 complex. It is the stoichiometric condition that causes the InP materials grown from P-rich melts higher carrier concentration than that of In-rich InP. The extra donor is hydrogen indium vacancy complex.The concentration of VInH4 in Fe-doped InP is higher than that of undoped InP. The concentration of VInH4 is high in wafers from the top of an ingot and low from the tail of an ingot. The influence of this complex on the electrical properties of n-type LEC undoped and compensation in Fe-doped InP is discussed. The results reveal the influence of VInH4 on the thermal stability of InP material due to the fact that bond of hydrogen complex is weak and dissociates easily upon annealing.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.