Low resistance tunnel junctions with type-II heterostructures

Abstract

We propose tunnel junctions with type-II heterostructures to reduce the electrical resistance of vertical-cavity surface-emitting lasers. We fabricated the type-II tunnel junctions on GaAs substrates, which consist of highly C-doped GaAsSb on the p side and highly Si-doped InGaAs on the n side. We achieved an extremely low specific resistance of 4×10−6Ωcm2, which corresponded to a resistance of 20Ω for an aperture 5μm in diameter. The specific resistance of the type-II tunnel junction was about 40% smaller than that of the type-I tunnel junction.

Metamorphic Ga0.76In0.24As/GaAs0.75Sb0.25 tunnel junctions grown on GaAs substrates

“…As can be observed, for materials lattice matched to InP (Ga 0.47 In 0.53 As/GaAs 0.51 Sb 0.49 ) the band discontinuities are larger than for compositions of materials closer to the GaAs lattice constant. Since the tunneling barrier height and width depends on these discontinuities, 15 the tunneling probability enhancement provided by the type-II alignment should be less pronounced in our tunnel junction. This obviously affects the tunnel junction performance, as will be shown in Sec.…”

“…13,14 Moreover, another benefit of using this material in a GaInAs/GaAsSb tunnel junction is the type-II band alignment that these structures exhibit, which is reported to facilitate the tunneling of carriers via a lower tunneling barrier. 15 Pseudomorphic GaAsSb/ GaInAs structures were developed in the past for InP-based tandem solar cells, 16 achieving extremely high peak current densities over 19 kA/cm 2 . State-of-the-art Ga 0.47 In 0.53 As/ GaAs 0.51 Sb 0.49 tunnel junctions lattice-matched to InP substrates exhibit peak tunneling currents over 572 kA/cm 2 .…”

“…16 As tunnel junctions grown on GaAs substrates were developed for VCSELs structures working at lasing wavelengths as high as 1.1 lm, demonstrating the advantage of using a type-II band alignment. 15 In this work, we present the development of a high performance metamorphic Ga 0.76 In 0.24 As/GaAs 0.75 Sb 0.25 tunnel junction grown on GaAs. The band offsets in this system, which determine the tunneling probability, are calculated and used to compare its performance to existing pseudomorphic or lattice-matched tunnel junctions.…”

1.1-¿m-Range Tunnel Junction VCSELs with 27-GHz Relaxation Oscillation Frequency

“…The BTJ structure enabled us to replace a relatively high-resistive p-layer with the low-resistive n-type spacer and to decrease the chip resistance [4]. Moreover, a small specific resistance of 4 x 10-6 Qcm2 was achieved with the proposed type-II TJ of n-InGaAs/p-GaAsSb [5]. In addition to these reductions in resistance, for high-speed operation, differential gain is expected to increase because current injection uniformity is improved by electron injection with high mobility [6].…”

Sidewall GaAs tunnel junctions fabricated using molecular layer epitaxy

“…Later, tunnel junctions have been fabricated using Si [2,3], Si/SiGe [4,5], GaAs [6][7][8][9][10][11][12][13][14][15], InAs/Si [16], GaInAs/GaInNAs [17], InP/InGaAs [18], GaAsSb/InGaAs [19] and InAsP/GaAsP [20]. These tunnel junctions found numerous applications.…”