Diamond Doping by Low Energy Ion Implantation During Growth
- PDF / 342,461 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 111 Downloads / 270 Views
DIAMOND DOPING BY LOW ENERGY ION IMPLANTATION DURING GROWTH
K.D. Jamison, H.K. Schmidt, D. Eisenmann, and R.P. Hellmer, S.I. Diamond Technology, Inc., 2435 North Blvd., Houston, TX 77098
ABSTRACT A novel method of implanting dopant material in diamond using low energy ions during growth is described. In this method, relatively low energy (-10 KeV) dopant ions are directed through an aperture into a hot filament chemical vapor deposition growth chamber and onto the growing diamond sample. Collisions with the gas molecules in the growth chamber (-10 Torr of a 99.5% H2 - 0.5% CH4 gas mixture) partially neutralize the ion beam and slow the dopant atoms down to a few hundred electron volts before striking the growing diamond crystal. The residual energy is large enough to embed the dopant atoms a few layers deep in the crystal but not large enough to cause significant lattice damage. Continued doping during growth yields uniformly doped material throughout the implanted region. Results for sodium, rubidium, and phosphorus atom doping are presented with sodium found to be a p-type dopant and phosphorus a deep ntype dopant. INTRODUCTION Diamond has extremely high thermal conductivity, a large bandgap, high carrier mobilities and low neutron and ionizing radiation dislocation cross sections 1 . These physical properties make it a useful material from which to construct electronic devices for use in high temperature, Two significant problems impede high frequency and /or high radiation environments. development of electronic devices made using diamond -- lack of large single crystal substrates for mass production and no proven method for production of high quality n-type semiconducting diamond. This paper presents a possible solution to the second problem. Dopant incorporation into diamond has, to date, been a difficult problem. Boron, nitrogen and phosphorus have been substitutionally grown into the diamond lattice during CVD growth. Boron is electrically active, providing p-type material with an activation energy of -0.37eV 2,3, while nitrogen induces a deep level at 1.7eV 4 . Phosphorus doping has been reported, but to date has produced material with a rather high resistance in a polycrystalline film 5 ,6 . High energy ion implantation of lithium into diamond has met with limited success. The Li doped n-type behavior is not stable because the lithium tends to diffuse out of the sample after prolonged annealing 7 . To date, this method has produced highly compensated material with poor electrical conductivity due to lattice damage 8 ,9. which cannot be annealed out since the annealing temperature is above the graphitic conversion point of diamond. Pfins1° has used carbon ion induced lattice damage to produce n-type behavior in diamond. Unfortunately, this damage reduces the carrier mobility and will ultimately reduce the device performance. An alternative method of incorporating dopant atoms into diamond by implanting low energy ions into the sample duringgrowth is demonstrated in this paper. The procedure is similar to
Data Loading...
