Biomedical subjects

H Morkoc

Publications and source records attributed to H Morkoc.

18 recordsLinked to original sources

PubMed2006

Electric field modulation of infrared absorption at room temperature in electrochemically self assembled quantum dots.

We report observation of electric-field-modulated infrared absorption at room temperature in electrochemically self-assembled CdS quantum dots produced by electrodepositing the semiconductor in 50-nm pores of an anodic alumina film. The absorption is associated with photoassisted real space transfer of electrons from the CdS dots to surrounding trap sites in the alumina. Similar absorption was observed in the past [Appl. Phys. Lett. 79, 4423 (2001)] and was the basis of a room temperature near infrared photodetector. An electric field modulates this absorption by altering the overlap between the wavefunctions of electronic states in the quantum dots and the trap states in the surrounding alumina, thereby affecting the matrix element for radiative transitions, similar to the quantum confined Stark or Franz-Keldysh effect. The ability to electrically modulate absorption in these structures can result in inexpensive infrared signal processing devices operating at room temperature.

Crystallization↗

PubMed2004

Screw dislocations in GaN grown by different methods.

A study of screw dislocations in hydride-vapor-phase-epitaxy (HVPE) template and molecular-beam-epitaxy (MBE) overlayers was performed using transmission electron microscopy (TEM) in plan view and in cross section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

Gallium↗

PubMed1996