Investigation of GaAs Doping Superlattice Structure

Abstract

The doping superlattice (DS) concept requires, however, that (i) a considerable potential modulation is achieved on a (ii) short length scale. The Moping technique is well suited to achieve such a considerabIe potential modulation on a short length scale, since delta doping allows us to accomplish (i) high doping concentration (>lo13 cm-2) and a (ii) localization of impurities on a length scale of the superlattice constant. Thus, these properties of the Moping technique made possible the growth and characterization of the Esaki-Tsu type doping superlattice. Here, we pay a great attention to the long period DS structure, in which an interesting S-shaped negative-differential-resistance (NDR) phenomenon resulting from the avalanche multiplications within superlattice periods was obtained . The append outline in Fig.1 shows the band profile of a double-period DS structure. A linear-potential approximation is used to described the zigzag potential barriers in the DS region. Solving the Schrddinger equation : where h is the reducedPla&k's constant and the effect mass m* is equated in dl potential regions. We get the wave function in the zero-potentid region with n = I and VI, where k=~~/h, and C, and D, are the constant coefficients of the wave function in nth period, respectively. However, in the DS region, with a proper coordinate transformation, the wave function can be described by using the Airy functions Ai(z) and Bi(z), @n(z) = C,eikz + Dne-ikz (2)