Piotr M. Mensz

Blue‐green injection lasers containing pseudomorphic Zn1−xMgxSySe1−y cladding layers and operating up to 394 K

We describe the performance of blue‐green injection lasers containing Zn1−xMgxSySe1−y cladding layers. The devices have yielded the lowest reported threshold current densities (500 A/cm2) and the highest reported pulsed output powers (500 mW) at room temperature. Lasing has been observed at temperatures as high as 394 K. The room temperature and 85 K lasing wavelengths are 516 and 496 nm, respectively. The use of Zn1−xMgxSySe1−y, instead of ZnSzSe1−z, cladding layers provides a clear improvement in optical confinement, demonstrated by the widening of the far‐field pattern in the direction perpendicular to the layers. The lasers are separate‐confinement heterostructures with a ZnS0.06Se0.94 waveguiding region and a single Cd0.2Zn0.8Se strained quantum well. The entire structure is pseudomorphic with the GaAs substrate.

BeTe/ZnSe graded band gap ohmic contacts to p‐ZnSe

BeTe is not a very well known wide‐band semiconductor. Due to the close lattice match to GaAs and ZnSe and p‐type as‐grown character, BexZn1−xTexSe1−x graded band‐gap layers appear an ideal candidate for ohmic contact to p‐type ZnSe based semiconductors. These contacts allow for an implementation of epitaxial structures of II‐VI compound diode lasers entirely lattice matched to the GaAs substrate. The numerical calculations predict contact resistivity of BexZn1−xTexSe1−x graded gap contacts lower than ρc=10−4 Ω cm2 at acceptor doping level 1×1018 cm−3, which corresponds to a voltage drop across the contact layer of less than 0.1 V during lasing operation.

Electrical characterization of p‐type ZnSe:N and Zn1−xMgxSySe1−y:N thin films

Differential van der Pauw–Hall effect and resistivity measurements have been performed to determine the concentration and mobility of free holes in nitrogen doped ZnSe and Zn1−xMgxSySe1−y thin films. Hall data taken between 120 and 300 K, with magnetic fields up to 4 kG yielded an activation energy of the nitrogen acceptors in ZnSe:N of 104 meV. Donor compensation in the ZnSe:N samples was negligible. Compared with ZnSe:N, samples of Zn1−xMgxSySe1−y:N, exhibited a significantly lower value of room‐temperature mobility of holes, and fast‐carrier freeze‐out at relatively high temperature, approximately T=200 K.

Charge injection frequency multiplier

We propose a novel frequency doubler, implemented in three terminal semiconductor heterostructures. This device represents a natural embodiment of the symmetry of hot‐electron injection with respect to the polarity of the heating voltage. An efficient frequency doubling, comprising conversion gain with low harmonic distortion of the output signal was demonstrated using InGaAs/InAlGaAs/InGaAs charge injection transistor devices. A natural extension of this idea is the implementation of a higher order frequency multiplier and a frequency mixer.