Determination of Lateral Extension of Extrinsic Photon Recycling in p-GaN by Using Transmission-Line-Model Patterns Formed with GaN p--n Junction Epitaxial Layers

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The effect of extrinsic photon recycling (EPR) in p-type gallium nitride (p-GaN), namely, increased ionization ratio (R) of magnesium acceptors owing to radiative recombination, was quantitatively investigated. The lateral extension (L) of EPR was determined by using transmission-line-model (TLM) patterns, formed with GaN p--n junction epitaxial layers on free-standing substrates, as well as by using device simulation. With increasing vertical current (I_{\text{V}}) of the p--n junction, lateral current (I_{\text{L}}) in the p-GaN layer (magnesium concentration: N_{\text{Mg}} = 5\times 10^{17} cm<sup>-3</sup>) was found to increase within L of 10 μm from the edge of the TLM electrodes; the measured I_{\text{L}} corresponded to a large R, namely, 30%. This lateral extension will contribute to reducing base resistance and enhancing conductivity modulation of GaN bipolar power-switching devices for power-electronics applications.
2013-08-25