Highly Phosphorus-Doped Polycrystalline Diamond Growth Using Pulsed Gas Conditions

The production of high-quality phosphorus-doped diamond layers is crucial for the
development of diamond-based electronic devices such as PIN diodes and fieldeffect
transistors. In this work, phosphorus-doped polycrystalline diamond layers
were grown by MicroWave Plasma Enhanced Chemical Vapor Deposition
(MWPECVD) using a new gas control process involving pulsed CH4 flow to increase
the incorporation of phosphorus in diamond. Using this method, high quality
polycrystalline phosphorus-doped diamond layers with a sp3/sp2 carbon ratio over
75% were grown on Si substrates. The phosphorus concentration, measured by
Glow Discharge Optical Emission Spectroscopy, reaches a record high value well
above 1020 cm-3. Additionally, to better understand the dynamics of precursor gases
in pulsed growth conditions, the dynamic response of different gases (N2, CH4, and
O2) impulses in hydrogen plasma was studied in two different MWPECVD reactors: a
lab made NIRIM type reactor, and a commercial reactor made by Seki Diamond
Systems. These reactors of different volumes were operated at different pressure
and total gas flow. The time responses to the precursor gas injection were recorded
by Optical Emission Spectroscopy (OES). Experimental time responses were fitted
using an impulse response equation. Fitting parameters were extracted and
compared for the different reactors, gases, total gas flow, and pressure conditions.
The time responses of the different reactors were discussed as a function of their
volume and the operating conditions.