High Field Mobility

Fig. 1: Distribution function of electrons in GaAs(1-x)N(x) with x = 1.2% at F=10 kV/cm.
Fig. 1: Distribution function of electrons in GaAs(1-x)N(x) with x = 1.2% at F=10 kV/cm.

Materials Theory Group > Transport and Atomic Structure in Semiconductor Alloys > Dilute Nitrides > High Field Mobility

It is well established that replacing As by N in GaAs1-xNx leads to a strong perturbation of the conduction band structure, commonly described using the band-anticrossing (BAC) model [1]. This strong perturbation also leads to a marked reduction in low-field electron mobility [2], and has been predicted to suppress electron multiplication in avalanche photodiodes (APDs) [3]. In order to address the high field mobility in GaAs1-xNx, we have solved the Boltzmann equation [4] using two different band structure models. First, we considered carriers in parabolic G and L bands of GaAs, including polar optical phonon (PO), and intervalley phonon scattering in both valleys and investigate the effect of resonant scattering by nitrogen states [2]. Second, we assumed carriers constrained in the lower band of the BAC model, including phonon scattering and scattering by localized nitrogen states. By using a parabolic band structure, the first of these models is expected to underestimate the effects of N, while the second approach prevents carrier acceleration to higher energy, and must therefore overestimate the effects of N.

Figure 1 compares the calculated spherically symmetric part of the electron distribution function for the different models at an electric field of F=10 kV/cm. In this figure, curves (a) and (b) depict the results for the parabolic G band of GaAs without, and with energy-dependent N scattering (x=1.2%), respectively. It can be seen that the inclusion of isolated and pair N states strongly suppresses the acceleration of electrons to higher energy. This plot also shows the distribution functions calculated using (c) the BAC model with polar-optic scattering only, and (d) the BAC model with N scattering, for GaAs1-xNx (x=1.2%).

Figure 2 shows the calculated variation of drift velocity for GaAs1-xNx with x=1.2%, for models explained in Fig. 1. Fig. 2(a) shows the calculated drift velocity for GaAs, which is very similar to previously measured and calculated values for GaAs.

Including N scattering in (b) moves the peak of the negative differential velocity (NDV) to higher electric field, and pushes its value down. Fig.2 (c) and (d) compare the effect of scattering in the BAC model. This model has a better description for electron transport at lower electric fields. However, it underestimates the drift velocity at higher fields.

Comparing curves 2(b) and (d), we conclude that the inclusion of N scattering strongly suppresses the possibility of negative differential velocity in GaAs1-xNx, in agreement with experiment [5], but contrary to a previous simpler model, which used dynamical balance equations with a simplified description of N scattering [5]. Finally, we shall also discuss briefly the consequences of these calculations and of recent band structure calculations [6] for electron multiplication in GaAs1-xNx, APDs.

 

Related people

    Masoud Seifikar
    Stephen Fahy
    Eoin O'Reilly

  

Related publications

Analysis of band-anticrossing model in GaNAs near localised states
M. Seifikar, E.P. O’Reilly and S. Fahy,
Physica Status Solidi B, 248: n/a. doi: 10.1002/pssb.201000784 (2011)

 

Related presentations

M. Seifikar, E.P. O'Reilly and S. Fahy, Theory of Scattering and Impact Ionization in Dilute Nitride Avalanche Photodiodes,
EMRS, Strasbourg 2010

M. Seifikar, E.P. O'Reilly and S. Fahy, Analysis of Band-Anticrossing Model in GaAs1-xNx Dilute Nitride Alloys,
14th Irish Nanoscale Simulators Meeting, 2011

M. Seifikar, E.P. O'Reilly and S. Fahy, Theory of Scattering and Impact Ionization in Dilute Nitride Avalanche Photodiodes,
Inspire video conference seminars, 2010

M. Seifikar, E.P. O'Reilly and S. Fahy, High Field Transport in GaAs1-xNx Dilite Nitride Alloys (poster),
Fabrication to Application Workshop, Tyndall National Institute, 2010

M. Seifikar, E.P. O'Reilly and S. Fahy, Theory of Scattering and Impact Ionization in Dilute Nitride Avalanche Photodiodes (poster),
Joint CECAM Nano-Structures Workshop, Tyndall National Institute, Ireland / University of Manchester, UK

M. Seifikar, E.P. O'Reilly and S. Fahy, High Field Transport in GaAs1-xNx Dilite Nitride Alloys (poster),
Photonics Ireland 2009, Kinsale, Ireland, 2009

M. Seifikar, E.P. O'Reilly and S. Fahy, Theory of Scattering and Impact Ionization in Dilute Nitride Avalanche Photodiodes (poster),
5th International Summer School New Frontiers in Optical Technologies, Tampere, Finland, 2009

 

Related pages

    Analysis of band-anticrossing model in GaNAs near localised states
    The Density of States in GaAs:N
    Mobility in GaAs:N
    Dilute Nitride Materials

 

References

[1] W. Shan, et al. Phys. Rev. Lett. 82, 1221 (1999).
[2] S. Fahy, A. Lindsay, H. Ouerdane and E. P. O’Reilly, Phys. Rev. B. 74, 035203 (2006).
[3] A.R. Adams, Elec. Lett. 40, 1086, (2004).
[4] E.M. Conwell, MO Vassel, Phys. Rev. 166, 797 (1968).
[5] A. Patanè, et al. Phys. Rev. B 72, 033312 (2005).
[6] M. Seifikar et al, physica status solidi (b), 248: n/a. doi: 10.1002/pssb.201000784 (2011)

Contact: 

Masoud Seifikar

Ireland fund ecsf ucc
Privacy - Legal Statements
Tyndall - All rights reserved - 2014