Development of High Performance Ohmic Contact Materials for Full Color Light Enitting Devices.

为了研究制备与p-GaN非反应（非合金化）欧姆接触的可能性，研究了GaN表面处理和接触金属的功函数对金属接触与p-GaN之间的电学性质的影响。在用金属有机化学气相沉积法生长的GaN衬底上发现了一层由GaO_x和吸附碳组成的污染层。在离子密度为~ 10-^2 μ A/cm^2的情况下，用Ar和N离子溅射GaN表面不能完全去除污染层。虽然通过浸泡在缓冲HF溶液中部分去除了污染层，但GaN/金属界面的电学性能几乎没有得到改善。通过在接近500 ° C的温度下对Ni和Ta接触进行退火，去除了大部分污染层。这些退火的接触显示出从接触金属到GaN的电流注入略有增强。目前的表面处理研究表明， ...更多信息 污染层的去除没有显著降低接触电阻。另一方面，当GaN上沉积Pt、Ni、Pd、Au、Cu、Ti、Al、Ta和Ni/Au时，电阻随金属功函数的增加呈指数下降，这表明p-GaN/金属界面处的肖特基势垒高度可能不钉扎在GaN表面。本研究的结论是，具有大功函数的接触金属对于p-GaN的非反应欧姆接触是理想的。然而，这些接触没有提供蓝光激光二极管所需的law接触电阻。此外，各种金属的肖特基势垒高度（SBH）用光电发射谱、电容-电压（C-V）、透射电子显微镜（TEM）和透射电子显微镜（TEM）对分子束外延生长的p-ZnSe（In、Cd、Nb、Ti、W、Cu、Ag、Au、Ni、Pt和Se）接触层进行了测量。和/或电流密度-电压（J-V）方法。由于单色入射光在p-ZnSe外延层中的强烈干扰，内光电能谱法不能准确测量这些金属的SBH。C-V方法测量的SBH值为Au接触的1.23 eV和Ni接触的1.13 eV，但由于C-V曲线的强滞后性而没有测量其它金属的SBH。用J-V法成功地测得这些金属的SBH为1.2（μ SY ±）。[)0.1本实验表明SBH值与接触金属的功函数无关，表明费米能级可以钉扎在p-ZnSe/金属界面处。此外，导通电压传统上用于评估接触金属的电性能被发现是非常敏感的SBH值。少

In order to examine the possibility of preparing an non-reacted(non-alloyed)ohmic contacts to p-GaN,the effects of GaN surface treatments and work functions of the contact metals on the electrical properties between the metal contacts and p-GaN were investigated. A contamination layr consisting of GaO_x and adsorbed carbons was found on the GaN substrate grown by metalorganic chemical vapor deposition. The contamination layr was not completely removed by sputtering the GaN surface with Ar and N ions where the ion densities were -10-^2 muA/cm^2. Although the contamination layr was partially removed by immersing in a buffered HF solution, little improvement of the electrical properties of the GaN/metal interfaces was obtained. Most of the vontamination layr was removed by annealing the Ni and Ta contacts at temperatures close to 500ﾟC.These annealed contacts exhibited slightly enhanced current injection from the contact metal to the GaN.The present surface treatment study indicated that … More removal of the contamination layr did not significantly reduce the contact resistance. On the other hand, the resistance decreased exponentially with increasing the metal work functions, where Pt, Ni, Pd, Au, Cu, Ti, Al, Ta, and Ni/Au were deposited on the GaN.This result suggests that the Schottky barrier height at the p-GaN/metal interface might not be pinned at the GaN surface. The present study concluded that a contact metal with a large work function is desirable for non-reacted ohmic contacts to p-GaN.However, these contacts did not provide the law contact resistance required for blue laser diodes.In addition, Schottky barrier heights(SBH's)of a variety of metals(In, Cd, Nb, Ti, W,Cu, Ag, Au, Ni, Pt, and Se)contacting to p-ZnSe grown by a molecular beam epitaxy method were measured by an intenal photoemission, capacitance-voltage(C-V)、and/or current density-voltage(J-V)method. The internal photoemission method could not measure accurately the SBH's of these metals due to a strong interference of the monochromatic incident light in the p-ZnSe epilayr. The C-V method measured the SBH value of 1.23 eV for the Au contact and 1.13 eV for the Ni contact, but did not measure the SBH's of other metals due to strong hysteresis of the C-V curves. The SBH's of these metals were successfully measured by the J-V method to be 1.2(]SY.+-。[)0.1 eV.The present experiment showed that the SBH values were independent of the work functions of the contact metals, indicating that the Fermi-level could be pinned at the p-ZnSe/metal interface. In addition, turn-on voltages conventionally used to evaluate the electrical properties of the contact metals were found to be very sensitive to the SBH values. Less