Carbon in High-Purity Germanium

Abstract

14,Using ^C-spiked pyrolytic graphite-coated quartz crucibles for the growth of nine ultra-pure germanium single crystals, we have determined the carbon con tent and distribution in these crystals. Using autoradiography, we observe a rapidly decreasing carbon cluster concentration in successively grown crystals. Nuclear radiation detectors made from the crystals measure the betas from the internal"^ decay ing l^c nuclei wiih close to 100Z efficiency. An average value for the total carbon concentration [14c+i:Cj is -2x10 14 cnr 3 , a valje substantially larger than expected from earlier metallurgical studies. Contrary to the most recent measurement, we find the shape of the beta spectrum to aqree very well with the statistical shape predicted for allowed transitions.can explain all the observed properties of several of the new centers has been proposed recently.s The model is based on a heavy, substitutional impurity such as copper, oxygen, silicon or carbon trapping a light, interstitial impurity such as hydroqen or lithium in its vicinity (Fig. 1), Th potential well which is trapping the interstitial m --ity is thought to be created by the difference in thi ond length of the substitutional impurity and the ger ianium host lattice. The "rapid quench" centers (as Hall called them) fit the above model and have been n?Tted accord ing to their composition A(H,3i) and D(H • (A stands fr.-acceptor, D for donor). Detector makers, can avoid the formatir.. ut these undesirable centers by cooling slowly after any heating cycle, better even by keeping the device at T = 160"C for 10 to 30 minute* 1 before returning to room temperature.

Hydrogen Concentration and Distribution in High-Purity Germanium Crystals

“…The total hydrogen concentration has been deter mined using the self-counting detector technique 16 Figure 1 is a schematic of the apparatus used in growing 3 H-doped crystals. A Czochralski crystal puller was assembled with a recirculating hydrogen purifier and a generation and recovery system for the 3 H. In order to minimize the total 3 H inventory, the interior volume was made to be less than one liter.…”

Germanium: From its discovery to SiGe devices

“…Overcharged double acceptors Be and triple acceptors Cu were created and studied through optical pumping [37,38]. The concentrations of carbon and of hydrogen in ultrapure crystals were determined by using radioactive 14 C or tritium during crystal growth, respectively, and making self-counting detectors [39,40]. All these discoveries and studies were made possible through the co-location of crystal growth and characterization and through collaborations with many outstanding colleagues.…”

A massive neutrino in nuclear beta decay?

“…Schematic view of the system used in the 55Fe IB experiment. 3 that a true "local" analysis could be performed. It is well known that taking the second derivative of a spectrum can sometimes reveal small peaks that might otherwise be missed.…”