Annealing effects on electrical properties of thermal neutron transmutation doped Ge

Abstract

A neutron transmutation doping technique was applied to the high purity n-type germanium with 50 Ω cm (n=5.9×1013/cm3). For a neutron flux density of 5×1011/cm2 s and an irradiation time of 60 min, the doped Ge was converted into p type with 7 Ω cm ( p=3.5×1014/cm3). By neutron irradiation it has been possible to introduce the shallow acceptors resulting from the damage in addition to gallium atoms as acceptors. The recovery of radiation damage was evaluated by the improvements of some electrical properties for various annealing stages. By annealing at 600 °C, a room temperature hole mobility of 2200 cm2/Vs has been achieved at p=6.2×1013/cm3 and ρ=45 Ω cm. And, also, we found that higher mobility holes in p-type Ge play an important role for the weak magnetic field as the lattice atoms recover from the radiation damage. Finally, the direct observation of the recovery of damage was performed by the measurement of channeling effects using a helium ion beam.

Photoluminescence study of Ge nanocrystals irradiated by reactor neutron flux

“…S 0 optical transitions in GeO color centers [21]. With increase Table 2 The impurity concentration of codoped Ge-ncs sample Neutron fluence (neutrons/cm 2 ) N Ga /N 0 N As /N 0 2.2 · 10 18 1.35 · 10 À6 4.02 · 10 À7 1.9 · 10 19 1.17 · 10 À5 3.47 · 10 À6 of annealing temperature, the energy of PL peak at 620 nm shifts to low-energy side, which is consistent with quantum confine effect. So the PL peak at 620 nm is related to exciton recombination luminescence [22][23][24].…”

“…The production rate of 75 As is 0.5 · 10 À2 atoms/cm 3 / neutrons/cm 2 . The isotope 77 Se is produced from reaction (6), but this isotope is the deep donor impurity which has level of 0.14 and 0.28 eV in the forbidden band and is not effective as the donor impurity [19]. Therefore, the net acceptor and donor concentration can be calculated by formula N impurity = N 0 k i d i ut, where N 0 is concentration of Ge atoms in the lattice (cm -3 ), k i is the abundance of isotope, u is the intensity of the thermal neutron flux (neutrons/cm 2 AE s), t is the exposure time (s), d i is the production rate of Ga and As.…”

“…First, this is highprecision doping, because the concentration of impurities introduced at a constant neutron flux is proportional to irradiation time, which can be controlled with a high accuracy. The second advantage is the high homogeneity of impurity distribution, which is determined by a random isotopic distribution, small neutron capture cross sections d i , and the uniformity of the neutron flux [18,19]. In this paper, p-type (Ga), n-type (As and Se) impurities codoping Ge-ncs were prepared by ion implantation, first thermal annealing, thermal neutron irradiation and second annealing.…”

Fabrication of uniform Ge-nanocrystals embedded in amorphous SiO2 films using Ge-ion implantation and neutron irradiation methods

“…8 Several attempts have been made recently to improve the uniformity of QD distribution. Neutron transmutation doping ͑NTD͒ is a technique which utilizes the nuclear reaction of thermal neutrons with the isotopes in a semiconductor material, [15][16][17] and it has been reported that impurities are distributed homogeneously in a material [18][19][20][21][22] by using NTD. Achieving uniform QDs under the 3D confinement conditions remains one of the most daunting challenges ͑in quantum-dot formation, etc͒.…”

Ion channeling and Raman scattering studies of the lattice disorder and residual strain in neutron irradiated GaN

“…The NTD method is used as a means of homogeneously introducing impurity atoms into semiconducting materials such as Si, a-Si:H [2], Ge [3], GaAs [4,5], GaP [6,7], InSe [8], GaS [9], GaN [10] and so on. Especially, NTD-Si has already been commercialized as a material for high power devices.…”