GaN-based diluted magnetic semiconductors, theory and experiment

Title: GaN-based diluted magnetic semiconductors, theory and experiment Author: Xu Daqing Degree-granting units: Xi'an University of Electronic Science and Technology Keywords: diluted magnetic semiconductor;; GaN;; ion implantation;; microstructure;; ferromagnetic Abstract: Diluted magnetic semiconductor (Dilute Magnetic Semiconductors, DMSs) as a good backup of spintronics
Materials, spintronics quickly become a neodymium magnets hot research materials. It has a semiconductor band structure, but also with the substrate lattice constant
Semiconductor similar, not only in the manufacture of the device can be a good time and compatible with existing semiconductor technology, and both magnetic properties.
However, DMSs study by the Curie temperature and low magnetic dopant solubility and other problems. 2000, Dietl and his co-
Zener model were based on theoretical prediction of GaN-based dilute magnetic semiconductors can reach the Curie temperature Tc above room temperature. The theoretical predictions
GaN-based raises the concern of diluted magnetic semiconductors. GaN-based diluted magnetic semiconductors can be used diffusion method, molecular beam epitaxy (MBE)
, Metal organic chemical vapor deposition (MOCVD) and preparation methods such as ion implantation. As the use of diffusion of the magnetic metals mixed
GaN is still limited by the solubility and requires a higher temperature and longer time, so I do not have practical value. As for the MBE and
MOCVD, how to solve the problem of doping solubility of magnetic elements has been a problem. As the ion implantation itself, the technical features and no solid
Solubility limits, etc., so prepare ion http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php implantation is an effective means of DMSs. Prepared using ion implantation of GaN-based DMSs,
Although there have been reported, but the vast majority of the samples only the magnetic properties of a simple report, and are based on the basic theory
Prediction of Mn-doped P-type GaN research, and unintentional doping of Mn ions into GaN is very little research, especially with material microstructure
Changes in characteristics of the structure of the magnetic properties of the sample analysis is still a subject to be studied in depth. In this context, the
Text-based first-principles density functional theory plane-wave pseudopotential method for Mn-doped GaN electronic structure and optical properties of the
Calculation and analysis, preparation of Mn ions into GaN-based micro-structure diluted magnetic semiconductor, optical, magnetic and electrical properties of the measuring system
Pilot study, the main results obtained are as follows: (1) First, based on first-principles density functional theory plane-wave pseudopotential method
Mn-doped GaN on the energy band structure, electron density of states and optical properties were calculated after analysis of the doping-related changes in the nature. Calculate
That, Mn doping as Mn3d and N2p orbital hybridization, resulting in spin-polarized impurity Dai, semi-metallic materials behave, if the impurity band
Carriers have sufficient mobility, from GaMnN can produce high polarization rate of spin-polarized carrier injection. In addition, Mn ion incorporation
Near the Fermi level provides a large number of carriers, changing the electronic transitions between the band, the dielectric function of GaN impact. Calculator
Ming, Mn-doped GaN, due to the Mn-doped with different impurities produced by the in-band transitions between states, optical absorption spectra in the emergence of new peaks
. The results also show that GaMnN electronic structure is more suitable for spin-polarized charge transfer, spin injection is a suitable source.
(2) Monte Carlo method, simulation software with Trim Mn ions of different energies of GaN into the average range, standard deviation and concentration
Degree distribution for the statistical calculations, simulated under different energy Mn ion implantation into GaN in the concentration distribution; design of Mn ion implantation
Into the preparation of GaN-based diluted magnetic semiconductor injection process parameters (energy and implantation dose) and annealing conditions. (3) of Mn from
GaN micro-injected into the sub-structure and optical properties. First, ion implantation of Mn-doped GaN micro unintentional structural and optical properties are studied
. With the XRD and found a alternative Ga and Mn atoms or Ga-Mn and Mn-N compounds with related characteristics. Using micro-Raman spectra of isolated
Child before and after annealing the sample before and after injection of micro-structural changes were studied, in addition to the peaks observed in GaN, the samples also appeared
Some new phonon modes and the peaks E 2high showing the shoulders on both sides of the peak effect. Analysis of emerging phonon modes are
Associated with the disorder activated Raman scattering (DARS), Ga, N vacancy-related defects in the vibrational modes and by Gax-Mny-related local vibration
(LVM) due. Lorentz transform-based sub-peak fitting method and about the quality of model-based analysis that E 2high shoulder peaks around
By the local structure associated with MnxNy local vibration (LVM) and (Ga, Mn) N LVM of Mn ions caused. Using photoluminescence
(PL spectrum) of the sample's optical properties are studied, tests showed there were two PL spectra associated with ion implantation at 2.53eV and
2.92eV luminescence peak of the new analysis that the emission band located at 2.92eV from the conduction band or the shallow donor level to the main level of the transition by
Compound produced by the radiation, and this may be by the main level with VGa related complex, the complex is located about energy gap energy level price
More than 0.4eV with the top position. For the green emission peak at 2.53eV, that is a shallow donor to the compound by the main transition radiation produced
Students. Of Mn ions into the Mg-doped GaN sample microstructure and optical properties. Test results and Raman spectra of unintentionally doped
Sample test results are basically the same. PL spectra showed that at 2.54eV and 2.9eV in addition to these two peaks, at 1.69eV
There is another new emission peak. Combined with the characteristics of Mg-doped GaN by PL spectra of the sample and 2.54eV 2.9eV peak intensity ratio of peaks
Analysis of changes with annealing temperature, that the emission peak at 2.9eV is MgGa-VN complexes (Dd) and Mg shallow acceptor formation of deep-Shi
Main - shallow acceptor related to the transition between the radiative recombination, and thus analysis of the emission peak at 1.69eV could be re-based MgGa-VN
Fit deep donor levels (Dd) and VGa complex related by the primary level (Ad) between the radiative recombination. (4) the ion
Into the GaN surface due to injury and different annealing temperatures damage repair. With the AFM result of ion implantation and surface damage of GaN
Annealing repair were analyzed, indicating that the GaN surface due to thermal decomposition at high temperatures, limiting the heat through the use of higher annealing temperature on the sample
Materials for effective repair. Research also shows that the use of heat to reduce the target into the ion implantation damage is an effective way. By
Raman spectra of A1 (LO) and E 2high peak shape and peak width at half maximum of the study evolution with annealing temperature, that the lattice damage caused by ion implantation
Wound repair can be divided into three stages: when the annealing temperature is not higher than 800 ℃, the ion implantation the sample began to recrystallization by ion implantation
The lattice damage caused by the beginning have been restored, with the annealing temperature gradually increased from 800 ℃ to 900 ℃, the lattice damage repair further
And ion implantation induced defects also gradually reduced. When the annealing temperature to 900 ℃ for more than, GaN epitaxial layer on the surface begins to decompose
. Repair and ferromagnetic properties from the lattice both at the same time consider that the best sample after ion implantation rapid thermal annealing temperature should be controlled
System at between 800 ℃ to 900 ℃. (5) of Mn ions into the unintentionally doped GaN samples of magnetic and electrical properties. Do not
Samples with annealing temperature and the magnetization hysteresis loop characteristics of the test show that after 800 ℃ annealing the sample to obtain the highest magnetic
Of strength, and room temperature, the sample still showed a clear hysteresis loop, indicating that the material has ferromagnetic properties at room temperature. Analysis of samples
Ferromagnetic properties are mainly derived from the (Ga, Mn) N, and GaxMny with one hand because of the formation of Ga vacancies, can lead to ferromagnetic interactions involved in the regulation
With the increase in hole concentration; other GaxMny phase also enhanced the ferromagnetic sample. Magnetization versus temperature curve further testing
Permit the preparation of the material in this experiment the Curie temperature above room temperature, the test shows that the sample magnetization with temperature trend is clearly divided into two
Part. This result further validates the front to make the (Ga, Mn) N and GaxMny ferromagnetic materials, the relative contribution of reasoning.
Samples of CV test and the test showed that ion implantation into the Hall of defects on the one hand the concentration of carrier impact, on the other hand
Reducing carrier mobility. Reduce the ion implantation induced defects, reduce defects on the properties of dilute magnetic semiconductors is a need
Continue to study the issue. (6) of Mn ions into the Mg-doped GaN samples of magnetic and electrical properties. Magnetic properties
Test results show unintentionally doped with Mn ions into GaN samples similar results, the sample after annealing at 800 ℃ to obtain the highest magnetic
Samples of strength and shows a room temperature ferromagnetism. Test results show that the sample magnetization was higher than Mn ions into the unintentionally doped
GaN samples. MT curves of the samples although the trend is divided into two parts, but unintentional and Mn-doped GaN samples implanted compare
Two changes in slope of the curve was significantly smaller. Analysis that this was mainly due to Mg-doped GaN samples to ensure high hole concentration
(Ga, Mn) N samples of ferromagnetic properties of the leading role. The use of Mg-doped GaN epitaxial films at 700 ℃ were only weakly active treatment
Therefore, when annealing the Mg ion doping will produce the secondary activation, so the sample after 800 ℃, 900 ℃ annealing treatment, as set
Concentration has increased to some extent, but when the annealing temperature higher than 900 ℃, the sample surface from the decomposition of the introduction of the electronic N vacancies,
Making the hole concentration decreased. Electrical test data basically reflect the trend of Mn ions into the Mg-doped GaN samples which
A feature. Degree Year: 2009