Amphoteric substitutionality and lattice distortion of Ge in InP

We have studied the electrical and structural properties of InP implanted with Ge ions (2×10¹⁵/cm²). The implantation was performed at both room temperature (RT) and liquid nitrogen temperature (LNT). After annealing at 850°C for 5 s, both sets of samples exhibited n-type conductivity. The n-type activation efficiency in the RT implanted sample was about a factor of 2 higher than that in the LNT sample (15% and 8%, respectively). Extended x-ray absorption fine structure spectroscopy (EXAFS) shows direct evidence of the amphoteric substitutionality of the Ge atoms in InP for both samples. The ratios of Ge on In sites to Ge on P sites, derived from the EXAFS results, are consistent with the electrical behavior of the samples. The EXAFS results also reveal that the Ge - In and Ge - P bond lengths in the RT sample are very similar to their theoretical values, but are very different from the original In - P bond length. A relaxation in the Ge - In bond is observed in the LNT sample, resulting in a Ge - In bond length very similar to the original In - P bond length.