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Manuscript Title: Interface simulation of strained and non abrupt III-V quantum wells. Part 2: energy level calculation versus experimental data.
Authors: C. Lamberti
Program title: PLSIMUL
Catalogue identifier: ADCN_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 93(1996)82
Programming language: Fortran.
Computer: VAX-6420.
Operating system: VMS v.5.3-1.
RAM: 14K words
Word size: 32
Keywords: Solid state physics, Other, Iii-v semiconductors, Time-independent Schrodinger equation, Staircase potential, Quantum wells, Photoluminescence, X-ray diffraction.
Classification: 7.7.

Subprograms used:
Cat Id Title Reference
ADCM_v1_0 BANDSTRAIN CPC 93(1996)53

Nature of problem:
Modern CBE and MOCVD machines shows technological problems in the execution of instantaneous switches, inducing at the interfaces of III-V heterostructures a composition gradient spread over some monolayers [3,6]. As a consequence of this the interface layers are strained on the substrate lattice parameter and cause a local change in the bands profile along the growth direction able to remove of the heavy/light hole degeneration [7]. The bands profiles used as input by this program have been previously computed using the program BANDSTRAIN [8]. PLSIMUL is able to compute the quantized energy levels and the respective wavefunctions for electrons, heavy and light holes in any In1-xGaxAsyP1-y/In1-zGazAswP1-w QW, therefore even calculation on intentionally strained QW structures can be performed. For each particle, the solution of the Schrodinger equation is obtained by the imposition of boundary conditions along the growth axis on the probability density, |Psi|**2, and on the probability density flux, -> -> -> j = ihbar/2m[Psi nabla Psi* - Psi* nabla Psi], at each monolayer of the well (i.e. Psi and 1/m dPsi/dz, where z is the growth axis and m is the effective particle mass in the monolayer of given chemical composition). IMSL subroutine DNEQNF [1] is used. This program has been presented at two conferences [2], while some results on the simulation of InGaAs/InP heterostructures has been given, without any details on the program, in refs. [3,4] and in a PHD thesis [5].

PLSIMUL is not able to simulate the consequences of the interface roughness to the photoluminescence emission of the sample. This problem has been treated in refs. [3,9].

Unusual features:
By modifying the MVW.DAT input file (generated by the program BANDSTRAIN [8]), it is possible to compute wavefunctions and respective hamiltonian eigenvalues any hypothetical particle of arbitrary mass trapped in any one dimension potential. This result can be obtained by approximating the potential with a stair case profile.

Running time:
Few seconds to some minutes depending on the interface complexity, on the number of coupled wells and on the initial guesses.

[1] IMSL Math/library User's Manual, version 1.0, Houston (Texas), 1987, p. 776.
[2] C. Lamberti, C. Papuzza and A. Antolini, in proc. 7th European Workshop on Molecular Beam Epitaxy, Bardonecchia (I), March 07-10, 1993; C. Lamberti, in proc. 2o Convegno Nazionale di Informatica Chimica, Bologna, February 16-18, 1994, p. 23.
[3] A. Antolini, P.J. Bradley, C. Cacciatore, D. Campi, G. Gastaldi, F. Genova, M. Iori, C. Lamberti, G. Morello, C. Papuzza and C. Rigo, IEEE J. Elect. Mat. 21(1992)233.
[4] A. Antolini, L. Francesio, L. Gastaldi, F. Genova, C. Lamberti, L. Lazzarini, C. Papuzza, C. Rigo and C. Salviati, J. Crystal Growth 127(1993)189.
[5] C. Lamberti, PHD thesis in Physics, Chapter 6, University of Turin, 1993.
[6] F. Genova, A. Antolini, L. Francesio, G. Gastaldi, C. Lamberti, C. Papuzza and C. Rigo, J. Crystal. Growth 120(1992)333.
[7] T.Y. Wang and G.B. Stringfellow, J. Appl. Phys. 67(1990)344.
[8] C. Lamberti, Comput. Phys. Commun., submitted.
[9] C. Lamberti, S. Bordiga, G. Cerrato, C. Morterra, D. Scarano, G. Spoto and A. Zecchina, Comput. Phys. Commun. 74(1993)119.