Giant shifts of photoluminescence bands in GaN
Giant shifts of photoluminescence bands in GaN
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DOI：
10.1063/1.5140686
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发表时间：
2020-02
影响因子：
3.2
通讯作者：
M. Reshchikov
中科院分区：
文献类型：
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作者：
M. Reshchikov
在GaN中，有时会观察到光致发光（PL）带随激发强度或温度的异常大的位移。特别是，在3.28 eV的最大值的紫外发光带是由于从导带（或浅施主）的浅MgGa受体的跃迁。在半绝缘的GaN样品中掺杂Mg，巨大的红移（高达0.6 eV）和扩大的PL带可以观察到与温度或激发强度的变化。在掺Zn的半绝缘GaN中观察到类似的PL行为。在GaN：Zn中具有最大值在2.9 eV处的蓝带归因于电子从导带或从浅施主到位于价带上方0.4 eV处的ZnGa受主能级的跃迁。在导电的n型GaN中，随着激发强度降低5个数量级，该PL带红移仅为7 meV，并且用施主-受主对模型解释了该移位。然而，在半绝缘GaN：Zn样品中，已经观察到随着激发强度的降低而逐渐偏移高达0.8 eV。最后，在高质量的未掺杂GaN样品中，黄色发光带的位移不超过7 meV，而在重掺杂Si的GaN中可以观察到超过0.1 eV的红移。巨大的位移归因于高电阻率或重掺杂的n型GaN中的电场的存在。
Unusually large shifts of photoluminescence (PL) bands with excitation intensity or with temperature are sometimes observed in GaN. In particular, the ultraviolet luminescence band with a maximum at 3.28 eV is attributed to transitions from the conduction band (or shallow donors) to the shallow MgGa acceptor. In semi-insulating GaN samples doped with Mg, enormous redshift (up to 0.6 eV) and broadening of this PL band can be observed with variation of temperature or excitation intensity. A similar behavior of PL was observed in semi-insulating GaN doped with Zn. The blue band with a maximum at 2.9 eV in GaN:Zn is attributed to electron transitions from the conduction band or from shallow donors to the ZnGa acceptor level located at 0.4 eV above the valence band. In conductive n-type GaN, this PL band redshifts by only 7 meV with decreasing excitation intensity by five orders of magnitude, and the shift is explained with the donor–acceptor pair model. However, in semi-insulating GaN:Zn samples, a gradual shift by up to 0.8 eV with decreasing excitation intensity has been observed. Finally, the yellow luminescence band shifts by not more than 7 meV in high-quality, undoped GaN samples, while a redshift by more than 0.1 eV can be observed in GaN heavily doped with Si. The giant shifts are attributed to the presence of electric fields in high-resistivity or heavily doped n-type GaN.