InGaN based micro light emitting diodes featuring a buried GaN tunnel junction

Abstract

GaN tunnel junctions (TJs) are grown by ammonia molecular beam epitaxy. High doping levels are achieved with a net acceptor concentration close to ∼1020 cm−3, thanks to the low growth temperature. This allows for the realization of p-n junctions with ultrathin depletion width enabling efficient interband tunneling. n-p-n structures featuring such a TJ exhibit low leakage current densities, e.g., <5 × 10−5 A cm−2 at reverse bias of 10 V. Under forward bias, the voltage is 3.3 V and 4.8 V for current densities of 20 A cm−2 and 2000 A cm−2, respectively. The specific series resistance of the whole device is 3.7 × 10−4 Ω cm2. Then micro-light emitting diodes (μ-LEDs) featuring buried TJs are fabricated. Excellent current confinement is demonstrated together with homogeneous electrical injection, as seen on electroluminescence mapping. Finally, the I-V characteristics of μ-LEDs with various diameters point out the role of the access resistance at the current aperture edge.

True-blue laser diodes with tunnel junctions grown monolithically by plasma-assisted molecular beam epitaxy

“…Promising results for new types of edge-emitting LD or VCSEL have been reported recently for hybrid MOVPE=MBE growth in which the active part of the device was grown by MOVPE and the p-n TJ was made by MBE. [8][9][10]20) The p-n tunnel junction was demonstrated for narrowbandgap materials in 1958. 21) The theory of the p-n TJ indicates that the transmission probability of carriers through such a junction depends on the depletion width.…”

Comparison of nonpolar III-nitride vertical-cavity surface-emitting lasers with tunnel junction and ITO intracavity contacts

“…1,47 Recently, a III-nitride micro-LED with a BTJ has been demonstrated, 48 proving that a similar technology could be used in III-nitride VCSELs as well. A number of material properties have prevented the wide-spread adoption of III-nitride TJs in LEDs and VCSELs generally.…”

“…55 There are two primary methods for overcoming these issues: (1) activate the p-GaN using a side-wall activation method, 55 or (2) growth of the n-type TJ layers using molecular-beam epitaxy (MBE). 27,48,[56][57][58][59][60] Sidewall activation has been demonstrated, however it shows limitations in activating large-area devices (300 µm × 300 µm mesa size). 55 Because VCSELs are very small devices (≤ 100 µm × ≤ 100 µm mesa size), it seems quite plausible that side-wall activation could be used to make high quality III-nitride TJ intracavity contacts for VCSELs using MOCVD, which would greatly simplify the processing and growth procedure, compared to the MOCVD-MBE TJ VCSEL method.…”

Progress and challenges in electrically pumped GaN-based VCSELs

“…Buried tunnel junctions have also been demonstrated to laterally confine the current 130 , and if the introduced structural step from the overgrown TJ transfers into the top DBR, it might also provide simultaneous optical guiding 132,133 .…”

“…GdN nanoislands have also been incorporated in the TJ interface to increase the tunneling through midgap states 128,129 . Very promising are the pure GaN TJs demonstrated recently which have been incorporated into LEDs 130,131 . They have shown low differential resistance for a complete device (low 10 -4…”