Hybrid tunnel junction contacts to III–nitride light-emitting diodes

Abstract

In this work, we demonstrate highly doped GaN p–n tunnel junction (TJ) contacts on III–nitride heterostructures where the active region of the device and the top p-GaN layers were grown by metal organic chemical vapor deposition and highly doped n-GaN was grown by NH3 molecular beam epitaxy to form the TJ. The regrowth interface in these hybrid devices was found to have a high concentration of oxygen, which likely enhanced tunneling through the diode. For optimized regrowth, the best tunnel junction device had a total differential resistivity of 1.5 × 10−4 Ω cm2, including contact resistance. As a demonstration, a blue-light-emitting diode on a ( ) GaN substrate with a hybrid tunnel junction and an n-GaN current spreading layer was fabricated and compared with a reference sample with a transparent conducting oxide (TCO) layer. The tunnel junction LED showed a lower forward operating voltage and a higher efficiency at a low current density than the TCO LED.

Electron transport properties of degenerate n-type GaN prepared by pulsed sputtering

“…Secondary-ion mass spectrometry and Halleffect measurements revealed that the doping efficiency of PSD n-type GaN is close to unity at electron concentrations as high as 5.1 × 10 20 cm 3 . A record low resistivity for n-type GaN of 0.16 mΩ cm was achieved with an electron mobility of 100 cm 2 V 1 s 1 at a carrier concentration of 3.9 × 10 20 cm 3 . We explain this unusually high electron mobility of PSD n-type GaN within the framework of conventional scattering theory by modifying a parameter related to nonparabolicity of the conduction band.…”

“…The excellent electrical properties presented in this letter clearly demonstrate the striking advantages of the low-temperature PSD technique for growing high-quality and highly conductive n-type GaN The physics of degenerate electrons in a partially filled conduction band of heavily doped n-type GaN has been extensively investigated because of the importance for reducing the parasitic resistance of nitride optical and electron devices. [1][2][3] Si is the most commonly used dopant for n-type GaN, and a room-temperature (RT) free-electron concentration of 3.6 × 10 20 cm 3 has been achieved in Si-doped GaN deposited using molecular beam epitaxy (MBE). 3 Ge is also used as an alternative dopant to Si.…”

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

“…Our TJ design allowed us to achieve a differential resistivity lower than 10 −4 Ω·cm 2 for current densities higher than 2 kA=cm 2 , which is very promising for LD applications and is one of the best results among those reported in the literature. 4,8,23,29) An interesting remark can be given from the comparison of the differential resistivities of the standard LD, TJ LD, and test TJ n=p ++ =n ++ structure. Figure 4 shows the differential resistivities of the standard PAMBE and TJ LDs (the I-V characteristics of which are depicted in Fig.…”

“…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.…”

“…[2][3][4][5][6][7][8][9][10] Efficient TJs may find very important applications in injecting holes into the p-type region of LDs and LEDs, and thus TJs can open new possibilities in the design and architecture of III-nitride devices. The implementation of TJs to interconnect LD structures grown on top of one another paves the way to high-power nitride devices.…”