Electrochemical removal of hydrogen atoms in Mg-doped GaN epitaxial layers

Abstract

Hydrogen atoms inside of an Mg-doped GaN epitaxial layer were effectively removed by the electrochemical potentiostatic activation (EPA) method. The role of hydrogen was investigated in terms of the device performance of light-emitting diodes (LEDs). The effect of the main process parameters for EPA such as solution type, voltage, and time was studied and optimized for application to LED fabrication. In optimized conditions, the light output of 385-nm LEDs was improved by about 26% at 30 mA, which was caused by the reduction of the hydrogen concentration by $35%. Further removal of hydrogen seems to be involved in the breaking of Ga-H bonds that passivate the nitrogen vacancies. An EPA process with high voltage breaks not only Mg-H bonds that generate hole carriers but also Ga-H bonds that generate electron carriers, thus causing compensation that impedes the practical increase of hole concentration, regardless of the drastic removal of hydrogen atoms. A decrease in hydrogen concentration affects the current-voltage characteristics, reducing the reverse current by about one order and altering the forward current behavior in the low voltage region. V C 2015 AIP Publishing LLC. [http://dx.

Efficient Electrochemical Potentiostatic Activation Method for GaN-Based Green Vertical-LEDs

“…Mg − H → Mg + H + (s) + e (by electric voltage) [1] Removal of hydrogen atoms from the Mg-H complexes is required to about 1.93 eV according to the earlier reports, which is approximately the sum of binding energy of Mg-H and the H + diffusion. 15,40 However, the removal of H + from the surface of the p-GaN layer is still a critical issue. Generally, the EPA process has a number of advantages over the RTA process for enhancing the bond breaking of the selective Mg-H complex and for removing the H + from the surface of the p-GaN layer through several paths, as shown in Eqs.…”

“…Since the enhancement had occurred in light output power and IQE for EPA LEDs, the improvement of I-V behavior indicates a reduced leakage current, which is closely related to the incorporated H-atoms. 15 Generally, increasing the holes concentration through breaking the Mg-H complexes leads to further radiative recombination events and less current leakage paths, which in turn could decrease the forward voltage by increasing the photon generation efficiency.…”

“…The hole concentration of the Mg-doped p-GaN layer (∼1 × 10 18 cm −3 ) is much lower than the electron concentration (∼5 × 10 18 cm −3 ) in a Si-doped n-GaN layer, which reduces the recombination rate and inconvenient IQE. 14,15 A p-type GaN layer grown by metal organic chemical vapor deposition with magnesium (Mg) doping, which is the most common acceptor impurity for p-type GaN, is electrically passivated. This is mainly attributed to the bonding between Mg atoms and hydrogen (H) atoms (predominantly from the decomposition of trimethylgallium [Ga(CH 3 ) 3 ] and NH 3 precursors during the growth period), forming electrically inactive Mg-H complexes during the MOCVD process.…”

Optimized Aluminum Reflector for Enhancement of UVC Cathodoluminescence Based-AlGaN Materials with Carbon Nanotube Field Emitters

“…One of the issues concerns the deepening of the Mg-acceptor level, which would make it difficult to deposit the high-conductivity p-type layer [ 7 , 8 , 9 , 10 ]. In addition, the poor structural quality of the AlGaN epitaxial layers would cause dislocations and create non-radiative defects that destroy the internal quantum efficiency of the LEDs [ 11 , 12 , 13 , 14 , 15 ]. Furthermore, these devices currently display low light extraction efficiency and output power [ 16 , 17 , 18 , 19 ].…”

Electrochemical Potentiostatic Activation for the Improvement of 270 nm AlGaN-Based UV-C Light-Emitting Diodes

“…We have demonstrated and suggested in previous reports that electrochemical potentiostatic activation (EPA) treatment is effective in improving the hole carrier concentration in p-type GaN-based LEDs. [14][15][16][17][18] The neutral Mg-H bond is broken down into Mg − and H + by chemical solvent in the EPA method under constant voltage; this mechanism eventually leads to various effects, such as increased internal quantum efficiency (IQE), an improved the leakage current value in the reverse current region, and an extended lifetime of LEDs.…”