Epitaxially stacked GaAs GaAlAs lasers using a low-resistance tunnel junction

Low-resistivity Ga(In)As tunnel junctions have been used to interconnect ep itaxially two separate confinement heterostructure (SCH) InGaAs/GaAlAs lase r structures. Laser structures consist of a 0.2 mu m GaAs optical cavity co ntaining three Ga0.88In0.12As strained quantum wells sandwiched within two 1.5 mu m thick Al0.45Ga0.55As n- and p-type cladding layers. P(I) character istic exhibits two different laser thresholds: one at 420 A cm(-2) and anot her at 760 A cm(-2). A reference laser sample shows a threshold current den sity of about 400 A cm(-2). The reason for the higher threshold current val ue of the top laser is unclear at present, Details of both growth aspects o f heavy doped tunnel diodes and optimum design of stacked laser diode struc tures are presented. (C) 1999 Elsevier Science B.V. All rights reserved.