Wyniki wyszukiwania - BazTech

1

Generation-recombination effects in high temperature HgCdTe heterostructure photodiodes

Jóźwikowska A., Jóźwikowski K., Rutkowski J., Orman Z., Rogalski A.

Opto-Electronics Review

|

2004

|

Vol. 12, No. 4

417-428

EN

The effect of built-in electric fields and misfit dislocations on dark currents in high temperature MOCVD HgCdTe infrared heterostructure photodiodes has been investigated. From experimental data results that the current-voltage characteristics at 240 K and 300 K indicate significant contributions from tunnelling effects, which dominate the leakage current mechanism for reverse bias greater than a few tens of milivolts. Standard theoretical models show that Auger generation-recombination processes determine dark current in high temperature HgCdTe photodiodes. But taking into account only Auger mechanisms much overestimated theoretical results are obtained. To explain this fact, a two-dimensional model has been developed to investigate the dark current mechanisms in the vicinity of the junction termination at built-in electric fields. Calculated profiles of the energy bands and electric field along different cross-sections of the photodiode indicate that the electric field achieves a maximum value of the order of mid 10⁵ V/cm in the area the junction termination at the HgCdTe heterointerface. In these regions the high density of misfit dislocations are observed too. The presence of high electric field in this area decreases the ionisation energies of trap levels located in region of dislocations core, and hence increases the efficiency of Shockley-Read-Hall generation-recombination process. In addition to diffusion, generation-recombination and trap assisted tunnelling mechanisms, our model include the Poole-Frankel and phonon-trap assisted tunnelling effects in calculations of dynamic resistance of the junctions. The best fit of experimental data with theoretical predictions for dynamic resistance versus temperature has been obtained for dislocation density in the bulk of HgCdTe layer equal to 5x10⁻⁷ cm⁻².

2

Analysis of VLWIR HgCdTe photodiode performance

Wenus J., Rutkowski J., Rogalski A.

Opto-Electronics Review

|

2003

|

Vol. 11, No. 2

143-149

EN

The performance of very long wavelength infrared (VLWIR) HgCdTe photodiodes at temperatures ranging from 77 K up to 150 K is presented. The effect of inherent and excess current mechanisms on quantum efficiency and dynamic resistance-area RA product is analysed. Different methods of determining the ideality factor are shown and among them the one based on the use of RA product versus bias voltage proves to be most reliable. At higher temperatures, however, the calculated ideality factor does not give any useful information about the nature of the p-n junction current due to significant influence of the series and shunt resistances. A comparison of the experimental data with the results of analytical and numerical calculations shows that the photodiodes with cut-off wavelength up to 14.5 um are diffusion-limited at temperatures exceeding 100K.

3

Photoelectric properties of HgMnTe photodiodes with ion etched p-n junctions

Kosyachenko L. A., Rarenko I. M., Weiguo S., Zengxiong L., Qibing G.

Opto-Electronics Review

|

2000

|

Vol. 8, No. 3

251-262

EN

Thotodiodes with p-n junctions formed by ion etching of p-Hg1-xMnxTe (x ≈1) are reported. The multielement photodiode arrays for mid-infrared region were fabricated using surface passivation, photolithography and three-layer metallisation processes. The absorption curves of the crystals found from optical measurements are treated within the Kane theory for semiconductors with highly nonparabolic energy bands. The parameters of the diodes are obtained from their electrical study. It is shown that due to strong degeneracy of the n+ - layer the Hg1-xMnxTe diode structure can be considered as one-sided abrupt n+ -p junction with the barrier height larger significantly than the semiconductor bandgap. The diode responsivity spectra are interpreted in the framework of model taking into account the generation of photocarriers in n+ - and p-regions as well as in the depletion layer. The diode photoresponsivity in the region of the photon energies below semiconductor bandgap is shown to be caused by the gentle slope of the observed absorption edge. Temperature measurements reveal essential peculiarities of carrier tunnelling in the diodes. Invoking the general expression for the tunnelling probability and taking into consideration the opposing flow of electrons allow the observed tunnelling decay at low reverse biases to be explained. The zero bias resistance-area product (RoA) for the Hg1-xMNxTe diodes with cutoff wavelengths 7-8 and 10-11um amount up to 20-30 and ~ 500 Ω cm2, respectively, indicating the photodiodes under study to be competitive with Hg1-xCdxTe photovoltaic detectors.

4

Studies of relationship between deep levels and RoA product in mesa type HgCdTe devices

Yoshino J., Morimoto J., Wada H., Ajisawa A., Kawano M., Oda N.

Opto-Electronics Review

|

1999

|

Vol. 7, No. 4

361-367

EN

The relationships between the figure of merit RoA representing the junction property and deep levels representing electric properties of semiconductors have been studied. RoA can be estimated by current-voltage (I-V) measurements. Deep levels can be estimated using spectral analysis of deep level transient spectroscopy (SADLTS). It has been confirmed that values of activation energies concentrate around 30 meV with the increase of RoA. This suggests that the influence from the inherent deep levels in the HgCdTe device becomes strong due to the increase of RoA, resulting in the improvement of the diode characteristics.