I–V characterization of a quantum well infrared photodetector with stepped and graded barriers

► Zero-bias activation energy found from temperature dependent I–V measurements. ► Ground state energies and conduction band discontinuities were estimated. ► Ground states calculated by transfer matrix technique. ► Ground state lowering due to electron–electron interaction considered. I–V characterization of an n-type quantum well infrared photodetector which consists of stepped and graded barriers has been done under dark at temperatures between 20–300K. Different current transport mechanisms and transition between them have been observed at temperature around 47K. Activation energies of the electrons at various bias voltages have been obtained from the temperature dependent I–V measurements. Activation energy at zero bias has been calculated by extrapolating the bias dependence of the activation energies. Ground state energies and barrier heights of the four different quantum wells have been calculated by using an iterative technique, which depends on experimentally obtained activation energy. Ground state energies also have been calculated with transfer matrix technique and compared with iteration results. Incorporating the effect of high electron density induced electron exchange interaction on ground state energies; more consistent results with theoretical transfer matrix calculations have been obtained.