Synthesis of High-quality Indium Phosphide Polycrystal using Horizontal Gradient-freeze Method
Indium phosphide(InP)polycrystals were synthesized using the horizontal gradient-freeze method.The influence of different temperature gradients on the ratio of polycrystals was analyzed,The results show that the crystals are indium-rich with a ratio of less than 97%when the temperature gradient is lower than 4 ℃/cm,and the crystals are stoichiometric with a ratio of more than 99%when the temperature gradient is above 5 ℃/cm.The impurities and electrical properties of the polycrystalline samples were analyzed using glow discharge mass spectrometry(GDMS)and Hall tests.The purity of stoichiometric InP polycrystals was greater than 99.999 99%;the carrier concentration was less than 8 × 1015 cm-3;the mobility was greater than 3 900 cm2·V-1·s-1.The impurities in the polycrystals primarily included Si,S,Fe,Cu,Zn,and As.The sources of the impurities and their effects on the properties of the materials were analyzed.