Identification of deep defects in high-resistivity undoped LEC-GaAs irradiated with protons

Abstract

Deep levels related to defects in high-resistivity undoped LEC-GaAs, generated during the growth and by low-fluence proton irradiation () are investigated by means of photo-induced current transient spectroscopy (PICTS). In order to compare effects from defects in the volume and defects in the surface of the material on PICTS observations, sandwich Schottky diodes and planar samples with two ohmic contacts on the front face were studied. Five main traps were observed. In addition to apparent activation energies, it is shown that the nature of carrier traps can also be identified. Irradiation with protons results in the creation of a new electron trap at nearly 0.72 eV below the conduction band. It is also shown that significant modifications in PICTS results may occur when changing the wavelength of the exciting light. In order to check the reliability of the deductions made from PICTS related to the nature of the observed traps, deep level transient spectroscopy (DLTS) measurements were performed under a permanent illumination of the sample. A general comparison and discussion are based on the results obtained from these different techniques.

Defect-induced overshoot of quantum Hall plateaus

“…This is because in the high dose samples the large concentrations of defects have localized the electrons and a complete freeze-out of the free carriers can take place at low temperatures. The result that large concentrations of defects are introduced by proton irradiation is consistent with earlier studies of defect generation by proton irradiation in GaAs [10][11][12][13]. It is also supported by our photoconductivity measurements in which spectra similar to those obtained from As Ga -related defects in GaAs [14] were observed in the samples irradiated with protons.…”

“…The defects that mediate the scattering must therefore be in a state which has a spin. This is in consistence with the fact that the overshoot effect was observed in our experiment only after the defects were introduced to the samples by proton irradiation and the fact that there exist many different irradiation-induced defects which can have various spin states [11][12][13][14]. We would like to mention that the above model is also in consistence with our very recent experiment [21] on the influence of a layer of selfassembled quantum dots on a nearby 2DEG in an InGaAs/InP quantum well.…”

Flight demonstration of inverted metamorphic triple-junction solar cells in space

“…Although the radiation responses of solar cells have been investigated so far, [17][18][19][20][21][22][23][24][25] the accurate EOL performance of space solar cell at mission end is extremely important for designing a paddle for satellites. It is essential that the prediction method for degradation accounts for a wide range of energies as well as conditions that resemble the space radiation environment where the particles enter the cell from various directions, although the ground-based radiation tests can rely only on normal incident monoenergetic particles.…”