Search

Temperature-dependent current–voltage (I–V), capacitance–voltage (C–V) measurements, and frequency-dependent C–V measurements have been carried out to investigate electrical properties of phosphorus (P)-doped n-type homoepitaxial diamond layers. We have fabricated lateral dot-and-plane (with ring-shaped-gap) Schottky barrier diodes. Frequency-dependent capacitance measurements revealed the existence of a deep donor level. C–V measurements deduced that the net donor concentration was 6.2×1017 cm−3 and the corresponding built-in potential was 4.0 eV, when the P concentration was 8.3×1017 cm−3. Phosphorus electrical activity was 0.75 in the P-doped diamond layer. The carrier thermal activation energy (the donor level) was evaluated to be 0.6 eV from the relation between the net donor concentration and the carrier concentration.

Simultaneous surface topography and conductivity/potential measurements were carried out on low-field-emission (1 V/μm) carbon films by combining conductive atomic force microscopy and Kelvin probe force microscopy. The current image showed that highly conducting sites and nonconducting regions coexisted on a micro- and/or nanoscale. Further, in situ I–V characteristics of both regions demonstrated that the conducting sites have an Ohmic property, whereas nonconducting regions have a degenerated Schottky property. When combined with the current image, the contact potential difference image showed that the conducting sites have a highest contact potential difference of 0.5 V, which implies the existence of a graphite phase. It is revealed that the conducting channels play an important role in the low-field-emission process. It is also suggested that the combination of conductivity and surface-potential measurements is an effective method for investigating complex-phase nanostructural surfaces.

Capture and emission processes of electron at phosphorus (P) donor in a n-diamond epilayer are analyzed by admittance spectroscopy. Dependence of temperatures on capacitance and conductance-frequency curves is well explained by Shockley-Read-Hall statistics. Thermal ionization energy and capture cross section of P donor are evaluated to be 0.54±0.02eV and (4.5±2.0)×10−17cm2, respectively. Broadening of the conductance-frequency curve is observed, which is believed to be due to a large Debye tail of electron distribution at a depletion layer edge.