GROWTH AND PROPERTIES OF 1,3 AND 1.5µm GaInAsP DOUBLE HETEROSTRUCTURE WITH DIFFERENT ACTIVE LAYER THICKNESSES

Abstract

The control of active layer growth of laser diode (L-D) and Edge Light Emitting Diode (E-LED) is very crucial because an optimum layer thickness is required for the optimised performance of these devices. Theoretical optimum thickness values are around 500-700°C for E-LED /l/ and 1500A for 1.3 or 1.55 µm L.D. /2/.We have studied the growth kinetics of 1.3 and 1.55 µm active layer of typical double heterostructure (D-H) grown by Liquid Phase Epitaxy with a two phase solution technique. By optimising the cooling rate of the furnace and the supersaturation of the melt we are able to reproduce active layer thickness as low as 500 A.The quality of the waveguide formed by the active layer of the D-H has been studied from the shape of the emitted beam in the plane perpendicular to the junction. For active layer thickness greater than 0.3 µm the light distribution can be described by the usual slab waveguide theory. However, for lower active layer thickness the light distribution has a complicated shape, especially for E-LED, which cannot be described by theory. Moreover, the study of threshold current density with active layer thickness shows that the experimental optimum value is higher than the theoretical one. For example at 1.55 µm, our best threshold current density, 1.5kA/cm2 is obtained for a 0.3 µm active layer thickness, the threshold current increasing for lower values.These two observations suggest that some non uniformities appear in very thin active layer. Their origin and their relation with growth conditions will be discussed.