Low-resistivity vertical current transport across AlInN/GaN interfaces

Abstract

Effects of n-type doping of Al0.82In0.18N/GaN heterostructures on the conduction band (CB) profile have been investigated. Doping concentrations well above 1019 cm−3 are required to reduce the large barriers in the CB. Experimentally, Si- and Ge donor species are compared for n-type doping during metalorganic vapor phase epitaxy. For Si doping, we find substantial interface resistivity that will strongly contribute to total device resistivity. Doping of AlInN is limited by either the onset of a self-compensation mechanism (Si) or structural degradation of the AlInN (Ge). Only by Ge doping, purely ohmic behavior of periodic AlInN/GaN layer stacks could be realized.

Highly reflective and conductive AlInN/GaN distributed Bragg reflectors realized by Ge-doping

“…A tailored comparative study of Ge-and Sidoping of periodic AlInN/GaN heterostructures is found in our previous publication. 14) In this work we demonstrate lowresistive Ge-doped AlInN/GaN DBRs with ohmic characteristics and with maximum reflectivities of 99%. Such Gedoped DBRs have the potential to lower the threshold-current density and to simplify the fabrication processes for GaNbased VCSELs.…”

“…For theoretical confirmation, we have already conducted band-profile simulations pointing out that a carrier density above 10 19 cm −3 is necessary both for GaN as well as for AlInN layers to screen efficiently the energy barriers in the conduction band profile at the AlInN/ GaN interface. 14) This means that the optimum Si-doped AlInN in ML1 and ML2 superlattice structures cannot reach the necessary doping concentration (1 × 10 19 cm −3 ) for efficient current transport through the superlattice.…”

“…Contrary to GaAs-VCSELs with highly conductive arsenide-based DBRs, AlInN/GaN-based DBRs usually exhibit a considerable electrical resistance due to large polarization fields and a significant conduction band offset between GaN and AlInN. 3,[11][12][13][14] In most cases of GaN VCSELs fabrication, intracavity contacts are applied, leading to a higher threshold-current density, lower optical confinement, a lower device performance and increased cost of the device fabrication process. 9,15,16) Doping of the AlInN/GaN DBR layers could solve this problem.…”

Formation of GaN mesas with reverse-tapered edge structures on a lattice-matched AlInN layer for a positive beveled edge termination

“…[17][18][19][20] Furthermore, the carrier concentration of AlInN can be increased up to ∼10 19 cm −3 by Si and Ge doping. 21,22) The specific contact resistance at the AlInN/GaN interface is as low as 1.5 × 10 −7 Ω cm 2 , 21) and the vertical direction resistivity of a 300 nm thick AlInN layer is as low as 5.8 × 10 −4 Ωcm 2 . 22) These attributes make AlInN a desirable candidate as a sideetching layer material to initiate the formation of reverse tapered edge of GaN for power devices applications.…”