Processes occurring during the formation of graded ZnSe/ZnTe contacts on p-ZnSe

Abstract

We show that the formation of ohmic contacts to p-ZnSe does not mainly depend on the exact design of the applied ZnSe/ZnTe grading, but rather on the temperature during contact growth and the thickness of the ZnTe cap layer on top of the grading. These facts demonstrate that a diffusion process dominates the contact formation. From the activation energy of the diffusion process we conclude that the diffusing species is nitrogen, which diffuses from the ZnTe cap into the underlying p-ZnSe. The nitrogen excess leads to an overcompensation in the ZnSe. Such an overcompensation process can be quantitatively described by the formation of compensating complexes involving two nitrogen atoms.

Electrical and optical properties of r.f. co‐sputtered ZnTe–Cu thin films

“…For a number of devices (e.g. the CdTe photovoltaic cells and the ZnSe blue laser diodes), p + -ZnTe has been used [1,2], as an interfacial layer that provides negligibly small valence band discontinuity with the material while being able to form a low resistance contact with metals through tunneling.Therefore, the properties of p-ZnTe thin films heavily doped with impurities such as Cu [3,4] and N [5] have been investigated. A number of preparation techniques, including sputtering [3,5] have been used.…”

Photoluminescence of δ-doped ZnSe:(Te,N) grown by molecular beam epitaxy

“…Use of these materials led to the fabrication of short wavelength-ultraviolet and violet ͑390-420 nm͒-laser diodes ͑LDs͒ and a wide variety ͑450-530 nm͒ of bright light emitting diodes ͑LEDs͒. 10 Jung et al 11 We have recently improved on this approach, using a modulation doping technique 12 that allowed us to achieve a net acceptor concentration ͓N A ϪN D ͔ϳ(4Ϭ6)ϫ10 18 cm Ϫ3 with average Te concentrations less than 3%, and as low as 0.5% in some samples. 2 Besides, LEDs show a ''spectral gap'' in the green-yellow, i.e., between 530 and 590 nm.…”

Heavily p-Type Doped ZnSe and ZnBeSe

“…The problem of Ohmic contacts is being addressed via use of a graded ZnSe/ZnTe superlattice inserted between the ZnSe : N bulk and the ZnTe : N cap layer [4]. However, these contacts are not very stable due to (i) N diffusion into ZnSe : N layer, where it forms compensating defects [5,6], and (ii) large lattice mismatch between ZnTe and ZnSe, resulting in formation of extended defects [7]. The problem of inadequate doping of the device structure has not been addressed up to now.…”