Study Of Defects Related With Stoichiometry In InP Crystals

With the development of the semiconductor industry, InP has represented more andmore obvious advantages. The stoichiometry of the melt can make a great influence on thedefects inside the crystals. The semi-insulating properties can be realized more easily innon-doped InP prepared under phosphorus-rich conditions. However, in P-rich InP ingots,there are many pores making serious impacts on the material properties. In this paper, theformation and structure of the pores were analyzed. The distribution of Fe in InP waferswas investigated by using non-contact resistivity measurement and photoluminescencespectrum. The surface morphology and energy dispersive spectrometer were instituted withscanning electron microscope. The crystalline quality of the sample was investigated withX-ray diffraction. The etch-pits of dislocations were revealed with Huber etching method.The thermal stress was measured with transmitted differential spectroscopy.Both resistivity and PL peak intensity exhibited a circular ring shape distribution. Atthe center of wafers, the resistivity was lower, while the PL peak intensity was higher thanthe edge. The solid-liquid interface was convex to the melt, so, the center of waferscrystallized earlier than the edge, which led to the lower Fe concentration.EDS results showed that there were more phosphorus than indium on the wall of pores,and it could be considered nearly stoichiometric at the areas without pores. XRD resultsindicated that crystalline quality around pores was much lower than the areas without pores.At the center and edge of the wafers, both EPD and thermal stress were higher thanother areas. The dislocations and thermal stress exhibited a circular ring shape distribution.Around the pores on P-rich InP wafer, EPD was much higher, and at most pores, thermalstress was much stronger correspondingly, but around a few pores, thermal stress wasweaker by contraries. We think it is because the residual thermal stress can be releasedalong the pores penetrating through the ingot during annealing.