SPECIFIC-HEAT OF NEUTRON-COMPENSATED HEAVILY-DOPED SI-P NEAR THE METAL-INSULATOR-TRANSITION

The specific heat of neutron-irradiated heavily doped Si:P (3.3-10(18)cm-3 less-than-or-equal-to N(D) less-than-or-equal-to 7.3.10(18) cm-3) was measured between 0.07 and 3K and in magnetic fields between 0 and 6T. The compensation ratio was varied systematically by isochronal annealing. Characterization was done by temperature dependent measurements of Hall coefficient and electrical resistivity. The specific heat displays a minimum of the linear coefficient gamma at the carrier concentration where the P impurity band is starting to be occupied. The concentration dependence of localized moments inferred from Schottky anomalies can be interpreted in terms of localized magnetic moments arising from the defect structure introduced by the irradiation and from P-derived electrons. As in uncompensated Si:P, local moments survive on the metallic side of the transition.