Ion Implantation of Boron in Diamond
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ION IMPLANTATION OF BORON IN DIAMOND
G.S. SANDHU, M.L.
SWANSON and W.K. CHU University of North Carolina, Department of Physics and Astronomy, Chapel Hill, NC 27599-3255, USA
ABSTRACT It has been a challenge to inject dopant atoms onto diamond lattice sites by because of the complications of ion damage and defect ion implantation, We re-investigated this topic by implanting clustering during annealing. boron ions into an insulating natural diamond ( type II-A ) which was preBoth of the implantations were performed damaged by carbon ion implantation. The amount of pre-damage was adjusted to at liquid nitrogen temperature. diamond to promote boron produce enough vacancies and interstitials in Samples were characterized by substitutionality during subsequent annealing. It was found that optical optical absorption and electrical measurements. absorption of the implanted samples strongly depends on the post implant obtained from electrical The activation energies sequence. annealing measurements match very closely to those due to boron atoms in natural p-type the fraction of showed that Photoconductivity measurements diamonds. remaining electrically active radiation defects in the implanted and annealed samples depends on the relative fluences of boron and carbon.
INTRODUCTION Diamond based semiconductor devices may turn out to be of significant to the unique physical and electronic properties of importance thanks now because of difficulties diamond. Few such devices have been realized till Standard doping techniques such as diffusion or introduction of in doping. impurities during crystal growth are not applicable because of the high temperatures required for the former and the absence of any reliable technique for the latter. Therefore, the most promising way to dope diamond in a So far, this method has controlled manner is by means of ion implantation. yielded only limited success [1,2] because it requires finding annealing conditions which will drive the implants into electrically active sites and restore the diamond crystal structure, a task which is complicated by the When the ion tendency of the damaged diamond to turn into graphite [3,4]. dose is low enough to prevent graphitization, very few of the dopant atoms end up in electrically active sites [1,4]. It has been shown [5,6] that boron is responsible for the semiconducting Consequently, it is very properties of p-type natural diamond (type II-B). desirable to use boron as a test case for achievement of implantation doping A number of groups have attempted of insulating natural diamonds (type II-A). to achieve p-type doping in natural diamonds by ion implantation of boron at room temperature [1,2] as well as at high temperatures [2] ( 1200 °C ), It was observed that although high followed by annealing up to 1400 °C. temperature implantation allowed higher doses of boron to be implanted with relatively less damage to the diamond lattice, it did not lead to higher This could result fractions of dopant atoms in electrically active sites. from the compensation
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