LQMI-loss, single-mode InO,5a Gao.47As/lno.52Allo.48As/lnP optical waveguides fabricated by Zn-induced impurity-induced layer disordering

Impurity-induced layer disordering (IILD) can create active and passive devices with very narrow lateral optical and electrical confinement through well-controlled implantations or diffusions. Optical waveguides, heterostructure lasers, and lateral heterojunction bipolar transistors (HBTs) have been realized by IILD.ie3 Optoelectronic integrated circuits (OEICs) consisting of lasers and fieldeffect transistors (FETs) have also been successfully fabricated by this technique.4 It is clear that IILD can be an important technique for defining complex structures and circuits using one-step epitaxy. Most of the work reported to date have been with GaAs-based heterostructures. For optical communication systems it is important to make devices and circuits that operate in the 1.3-1.7 pm spectral range, where InGaAs/ InAlAs and InGaAs/InP heterostructures hecome important. It is therefore necessary to demonstrate the viability of having IILD to define active and passive devices in these materials. We report here results from our study on Si and Zn-induced IILD in InGaAs/InAlAs superlattices and the properties of optical waveguides made with the disordered material. Our tirst experiments were the study of IILD in InGaAs/InAlAs superlattices grown by molecular beam epitaxy (MBE) using implanted Si ions. It was evident that a high doping level and/or high annealing temperature would be required to create complete disordering. However the lightly doped or undoped regions exposed to these high annealing temperatures will experience a significant amount of In concentration modulation.5 This is undesirable because the modulation adversely affects the optical and electrical properties of the InGaAs/InAlAs heterostructures. From the existing work of Kawamura et a1.6 it is expected that Zn-induced IILD of InGaAs/ InAlAs heterostructures could provide complete interdiffusions of Ga and Al at lower temperatures. The Zn-diffusion experiments were done with an InGaAs (35 A)/InAlAs (100 A) superlattice. The 74period superlattice was sandwiched between thick InAlAs cladding layers, grown by MBE on a ( 100) InP substrate. The Zn diffusion was carried out in an evacuated ( < 10 5 Torr) and sealed quartz ampoule containing a solid source of Zn3Asz. The sample was annealed at a temperature of 725 K for 1 h and the Al, Ga, and As compositions were measured using Auger depth profiling and are shown~ in Fig. 1. It can be seen that Ga and Al are completely intermixed. Low-temperature photoluminescence (T = 14 K) measurements shown in Fig. 2 on the superlattice sample before and after Zn diffusion, shows a blue shift in peak energy from 1.21 to 0.94 pm and full width half maximum (FWHM) linewidths increasing from 13.1 to 66 meV, which further indicate the transformation of the InGaAs/ InAlAs multilayer into a homogeneous InGaAlAs layer. Capacitance-voltage measurements indicate that the acceptor doping level due to Zn diffusion into an InGaAs sample