ZHENG Dong-mei, WANG Zong-chi, XIAO Rong-hui. Hydrogenic Donor Impurity States in a Cylindrical Wurtzite GaN Quantum Dot[J]. 发光学报, 2010,31(5): 628-634DOI:
Hydrogenic Donor Impurity States in a Cylindrical Wurtzite GaN Quantum Dot
Based on the framework of effective-mass approximation and variational approach
the binding energy of a hydrogenic donor impurity state is investigated theoretically as functions of the impurity position and the quantum dot size by employing a trial wavefunction with two variational parameter for a cylindrical wurtzite GaN/Al
x
Ga
1-
x
N quantum dot(QD) with finite potential barriers. The numerical results show that the donor binding energy of the hydrogenic impurity is highly dependent on the impurity position and QD size. When the built-in electric field is ignored or considered
the donor binding energy has a maximum value with moving the impurity position along the growth direction. The donor binding energy increases firstly
reachs a maximum value
then decreases with increasing the height and the radius of QDs. The strong built-in electric field induces an asymmetrical distribution of the donor binding energy with respect to the center of the QD. In particular
we find that the donor binding energy is insensitive to the dot height when the impurity is located near the top boundary(
z
0
=L/2
z
0
=L/4
)of the WZ GaN/Al
x
Ga
1-
x
N QD. And we compare the above results with previous calculation results using different trial wavefunction. The present results using two variational parameter wavefunction is better than the results given by previous two-parameter wavefunction. A good agreement between the present results using two variational parameter wavefunction and the results of the wavefunction with one variational parameter is found. Using the binding energy obtained from the present calculations
we further calculate the virial theorem number as a function of the quantum dot radius. Our present result coincides with the previous finding
so we may say that the present trial wavefunction with two variational parameter can describe better the internal motion of hydrogenic donor impurity state in the cylindrical wurtzite QD.
关键词
Keywords
references
Zhao F Q, Sa R L, Wu R T Y. Energy level of a hydrogenic impurity in nitride parabolic quantum well
. Chin. J. Lumin. (发光学报), 2005, 26 (6):719-722 (in Chinese).
Zhang M, Ban S L. Pressure influence on the Stark effect of impurity states in a strained wurtzite GaN/AlxGa1-xN heterojunction
. Chin. Phys. B, 2009, 18 (10):4449-4455.
Zhang M, Ban S L. Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure
. Chin. Phys. B, 2009, 18 (12):5437-5442.
Wu H T, Wang H L, Jiang L M, et al. The electric field effect on binding energy of hydrogenic impurity in zinc-blende GaN/AlxGa1-xN spherical quantum dot
. Phys. B, 2009, 404 (1):122-126.
Wu H T, Wang H L, Jiang L M. Effect of different effective mass and electric field on the electronic structure in GaN/AlxGa1-xN spherical quantum dot
. Acta Phys. Sin.(物理学报), 2009, 58 (1):465-470 (in Chinese).
Xia C X, Jiang F C, Wei S Y, et al. Hydrogenic impurity in zinc-blende GaN/AlGaN quantum dot
. Microelectr. J., 2007, 38 (6-7):663-666.
Zheng D M, Dai X Q. Binding energy of a hydrogenic-like impurity in GaN/AlxGa1-xN quantum dots
. J. Guizhou Normal University (Natural Sciences) (贵州师范大学学报,自然科学版) , 2006, 24 (1):64-68 (in Chinese).
Zheng D M, Wang Z C. Influence of an impurity on the binding energy for an cylindrical quantum dot
. J. Hebei Normal University (Natural Science Edition)(河北师范大学学报,自然科学版), 2009, 33 (2):193-197 (in Chinese).
Xia C X, Wei S Y, Zhao X. Built-in electric field effect on hydrogenic impurity in wurtzite GaN/AlGaN quantum dot
. Appl. Surf. Sci., 2007, 253 (12):5345-5348.
Dai X Q, Huang F Z, Zheng D M. Influence of Al content on exciton confined in GaN/AlxGa1-xN quantum dots
. Chin. J. Semicond.(半导体学报), 2005, 26 (4):697-701 (in Chinese).
Shi J J, Gan Z Z. Effects of piezoelectricity and spontaneous polarization on localized excitons in self-formed InGaN quantum dots
. J. Appl. Phys., 2003, 94 (1):407-415.
Goff S L, Stebe B. Influence of longitudinal and lateral confinements on excitons in cylindrical quantum dots of semi-conductors
. Phys. Rev. B, 1993, 47 (3):1383-1391.
Koh T S, Feng Y P, Xu X, et al. Excitons in semiconductor quantum discs
. J. Phys.: Condens Matter, 2001, 13 (7):1485-1498.
Xu X, Feng Y P. Excitons in coupled quantum dots
. J. Phys. Chem. Solids, 2003, 64 (11):2301-2306.
Levinshtein M E, Rumyantsev S L, Shur M S. Properties of Advanced Semiconductor Materials (Translated by Yang S R, Yin J Z)
. Beijing: Chemistry Industry Press, 2003, 1,42,66 (in Chinese).
Wang H, Farias G A, Freire V N. Interface related exciton energy blue shift in GaN/AlxGa1-xN zinc blende and wurtzite single quantum wells
. Phys. Rev. B, 1999, 60 (8):5705-5713.
Angerer R, Brunner D, Freudenberg F, et al. Determination of the Al mole fraction and the band gap bowing of epitaxial AlxGa1-xN films
. Appl. Phys. Lett., 1997, 71 (11):1504-1506.
Vurgaftman I, Meyer J R, Ram-Mohan L R. Band parameters for Ⅲ-Ⅴ compound semiconductors and their alloys
. J. Appl. Phys., 2001, 89 (11):5815-5873.
Martin G, Botchkarev A, Rockett A, et al. Valence-band discontinuities of wurtzite GaN, AlN, and InN heterojunctions measured by X-ray photoemission spectroscopy