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AMPS is a computer-based program in one-dimensional designed to simulate physics of transport in solid-state semiconductor devices. This applies the first principles of continuity equations and Poisson’s equations method to examine transport behavior of electronic and optoelectronic semiconductor device based structures. Such architectures of device can consist of or incorporate amorphous or crystalline, polycrystalline materials. AMPS numerically solve the three controlling equations for semiconductor devices (the Poisson equation, the equations of electron continuity, and the hole continuity) short of having any a-priori statements regarding the processes of regulation of transport in such devices. AMPS can be used with this general and precise numerical treatment to study various device structures, including the following [13]:

 Solar cells having P-n and p-i-n structures and detectors with homojunction and heterojunction;

 Homojunction and heterojunction of microelectronic structures of p-n, p-i-n, n-i-n and p-i-p;

 Designs of solar cells with multijunction;

 Microelectronic multi-junction structures;

 Structures for detectors with graded composition and solar cells;

 Microelectronic structures graded in composition;

 New microelectronic, photovoltaic and optoelectronic devices;

 Optional back layered Schottky barrier devices.

Information, such as J-V characteristics, can be achieved in the dark and under illumination using the solutions given by an AMPS simulation software. These can be measured as a temperature variable. Collection efficiencies can also be obtained for solar cell, as well as detector designs as a function of light bias, voltage, and temperature. Additionally, significant information, like electric field concentrations, free and trapped carrier populations, profiles of recombination, and current densities of individual carriers, can be found from the AMPS program as a function of position. AMPS can be used to evaluate transport in different types of device structures that may include amorphous, crystalline, or polycrystalline layers or combinations of these. AMPS is intended to analyze, model, and optimize microelectronic, photovoltaic, or optoelectronic device architectures.

AMPS incorporate the following:

 a contact treatment allowing thermionic emission, as well as recombination happening at contacts of the device;

 a generalized gap state model for bulk or interface distribution of density of states;

 both recombination processes, i.e., band-to-band recombination process and Shockley-Read-Hall recombination phenomenon;

 a model for recombination that instead of using the frequently-applied single recombination level method calculates Shockley-Read-Hall recombination transport with any inputted general gap state distribution;

 Fermi-Dirac statistics instead of Boltzmann statistics only;

 gap state concentrations calculated with real statistics for temperature instead of frequently used T = 0K method;

 a model for trapped charge, which accounts for charge in any inputted overall gap state distribution;

 a model for gap state, allowing energy variation of capture cross-section;

 distribution of gap states whose properties change with position;

 spatial variation of carrier mobility;

 spatial variation of electron and hole affinities;

 different mobility gaps and optical gaps;

 calculation of characteristics of the device as a function of temperature and also with or without illumination in both forward and reverse bias;

 analysis of device structures made-up utilizing single crystalline, multicrystalline, or amorphous materials or all three.

The transport physics of device can be described in three controlling equations when modeling microelectronic and optoelectronic devices: the equation of Poisson, the equation of continuity for free holes, and the continuity equation for free electrons. So evaluating transport properties turn out to be a challenge to overcome with solving three coupled nonlinear differential equations, each having two boundary conditions associated with it. In AMPS, these three equations together with the suitable boundary conditions are concurrently tackled, so as to achieve a set of three unknown state variables at each device level: the electrostatic potential, the quasi-Fermi level of the hole, and the quasi-Fermi level of the electron. The carrier quantities, currents, fields, and so on, can thus be determined from these three state variables. To ascertain these state variables, the computer uses the method of finite differences and also the Newton-Raphson methodology. Iteratively, the Newton-Raphson Method calculates the roots of a function or roots of a set of functions if these roots are given a suitable initial supposition. Through AMPS, the one-dimensional structure being studied is separated into sections by a network of grid points. Then for each grid point, the three sets of unknowns are solved. We note that, at the user’s discretion, AMPS requires the mesh to have adjustable grid spacing. As stated, after obtaining these three state variables as a function of x, band edges, recombination profiles electrical field, carrier populations, trapped charge, current densities, and any other data related to transport may be extracted.

First, AMPS measure the simple band diagram, built-in potential, electric field, trapped carrier populations, and free carrier populations found in a device if there is no bias (voltage or light) of any kind. These solutions obtained at thermodynamic equilibrium permit to “see what the device will look like.”

AMPS will then use such solutions obtained at thermodynamic equilibrium as starting presumptions for the iterative scheme that will contribute to the full characterization of a device structure under voltage, illumination, or both voltage and illumination bias. AMPS produce output, such as band diagram (which include quasi-Fermi levels), carrier populations, recombination profiles, currents, current-voltage (I-V) characteristics, and spectral response for device structures with different voltage, illumination or voltage and illumination bias [14–16].

Given the range of voltage bias in the window for specifying the conditions for voltage bias, this range of voltages applies to both the dark I-V and light I-V. If the user wishes to get a biased band diagram, he/she can open the selected biased window to give AMPS the value that must (1) lie in the voltage detailed in the previous window and (2) be constant with the previously selected voltage step.

The only distinction at the user input window between light and dark I-V is in the lighting process, the user has to check “light on.” AMPS received AM1.5 by default but the user may specify the photon flux and spectrum. A box called “light-x,” is provided as a neutral filter/concentrator. The absorption coefficient must be manually entered by the user. Yet AMPS provide the user with an alternative in the “E_opt” box to shift the absorption coefficient linearly. Because absorption coefficient information is not easy to obtain most of the time, this linear shift will help the user check the band gap adjustment. You can see details on the user interface.

If the user wishes to see the current produced at each wavelength, the “spectral response” box must be checked. With and without light bias, AMPS will always produce spectral response. The spectrum and the flux in the window of the spectrum determine the light bias. The user-defined spectrum, therefore, defines the range of the QE graph. Users can also adjust the frequency of the probe laser. At the defined voltage bias, AMPS will produce QE.