Refractory semiconductor of boron phosphide

Abstract

The single crystal growth of boron phosphide (BP) by employing the high pressure flux method and chemical vapor deposition (CVD) process is described together with characterization of the prepared BP and its electrical, thermal, semiconducting, and electrochemical properties. BP single crystals prepared by the high pressure flux method contain copper used as the flux, but they are promising for photocathode materials. BP single crystalline wafers prepared by the CVD process using Si wafer substrate contained autodoped silicon with the concentration of 1018−1020 atoms·cm−3, depending on the growth temperature and the substrate plane. The Si atoms which act as acceptors are incorporated at phosphorus sites in BP. The lattice constants determined by the Bond method explain the conduction type of BP. Some electronic transport properties such as donor and acceptor levels and lattice scattering process before and after thermal neutron experiments are clarified. The thermal conduction is limited by three-phonon processes. The formation of defects by thermal neutron irradiation and that of structural disorder by ion-irradiation are mentioned. Schottky diodes consisting of n–BP and Sb or n–BP and Au, which are denoted as n–BP–Sb and –Au, respectively, show excellent characteristics, and their barrier heights are independent of metals and two-thirds of energy bandgap, expected from the surface-state model. Finally, recent results on thermoelectric properties of sintered specimens are mentioned.

Representative hybrid model used for analyses of heat capacities of group‐IV, III–V, and II–VI materials

“…(3), however, some additional hightemperature C p (T) data are required. Unfortunately, one is concerned in thermo-chemical literature, particularly for BP, with rather large uncertainties between C p (T) values published by different authors [56,57] (as shown by differences up to an order of 4 J K À1 mol À1 , in the region (7) and (8)). …”

“…3). Nevertheless, it turned out to be possible of estimating, at least roughly, the general trend of a monotonic increase of the C p (T) curve for BP up to about 800 K. To this end we have performed a simultaneous least-mean-square fit of the relatively accurate low-temperature data set [55] in combination with the largely uncertain high-temperature data sets [56,57] (the latter having been included with significantly lower weights; see further remarks on this point in the Appendix D). In this way we have obtained for BP the approximate parameter set given in Table 1.…”

On melting of boron phosphide under pressure

“…The cell was pressure-calibrated at room temperature using phase transitions in Bi (2.55 and 7.7 GPa), PbSe (4.2 GPa), and PbTe (5.2 GPa). The temperature calibration under pressure was made using well-established reference points: melting of Si, NaCl, CsCl, Pt, Rh, Al 2 …”

Electrical and Thermal Properties of B12P2 Wafers

“…The boron monophosphide is well known as a refractory semiconductors (1,2), but the rhombohedral boron phosphide is a wide-gap (3.3 eV) semiconductor (3).…”