nextnano.NEGF - Software for Quantum Transport

nextnano.MSB

Summary and introduction

nextnano++

Software documentation

Examples

nextnano³

Software documentation

nextnanomat

Software documentation

nextnano GmbH

nnp:optics:internal_quantum_efficiency

Emission: Internal Quantum Efficiency

In this tutorial we demonstrate how to calculate the internal quantum efficiency of a multi-quantum well structure as a function of the applied forward bias.

Physics Model

nextnano++ is capable of simulating recombination processes such as Shockley-Read-Hall (SRH), Auger and radiative recombination. Only the radiative (direct) recombination process (spontaneous emission) generates photons. If radiative recombination $R_{\rm sp}(x)$ is summed up over the full device, it equals the total number of photons emitted from the device per second, the photocurrent: $I_{\rm photon}$.

$$R_{\rm sp}= c_r (n p- n_{\rm i}^2)$$

$$I_{\rm photon} = \int\limits_{V_0} R_{\rm sp} {\rm d}V$$

If the injected charge carrier current is $I_{\rm charge}$, then the internal quantum efficiency $\eta_{\rm qe}$ is

$$\eta_{\rm qe} = \frac{I_{\rm photon}}{I_{\rm charge}}$$

Input file structure

Drift Diffusion

recombination_model{
SRH            = yes       # Shockley-Read-Hall recombination
Auger          = yes       # Auger recombination
}


The internal quantum efficiency is calculated automatically when the radiative recombination is switched on

     radiative      = yes       # radiative recombination (direct recombination)


Results

Bandstructure

The band structure of the MQW structure can be seen in figure 1 without bias voltage.

Recombination

An example for the distribution of the recombination processes is plotted in figure 2

Current-Voltage Characteristics

The $I-V$ characteristics of the device is plotted in figure 3. This figure also includes the full photo current.

Quantum Efficiency

The internal quantum efficiency is plotted in figure 4