Ultraviolet photodetectors based on MgZnO thin films

Abstract

In this work, Ti/Au Ohmic contacts to both Mg0.24Zn0.76O and ZnO film-based metal-semiconductor-metal (MSM) photodetectors (PDs) were fabricated on glass substrates for comparative analysis. The transmittance spectra measured around the optical energy gap revealed that Mg0.24Zn0.76O films have a larger optical energy gap (3.54 eV) than ZnO films (3.25 eV). Mg0.24Zn0.76O MSM-structured ultraviolet (UV) PDs show a much higher UV-to-visible rejection ratio of 2.78×103 than those made of ZnO films. This can be attributed to the low dark current (0.08 pA) of the Mg0.24Zn0.76O UV PDs and the small full width at half maximum (0.34°) of the Mg0.24Zn0.76O (002) x-ray diffraction peak, indicating better crystal quality than that of ZnO. With an applied bias of 5 V and illuminations at 350 and 380 nm, the Mg0.24Zn0.76O and ZnO film-based MSM PDs exhibited responsivities of 0.4 and 0.32 A/W, respectively.

Dual-band MgZnO ultraviolet photodetector integrated with Si

“…As the BeO layer has been proven to be an ineffective carrier blocking layer in our previous reports, 17,18 it will be ignored in our following discussions on carrier transportation behavior in this multilayer structure. During the growth, the Mg Knudsen cell is controlled at 362 C, 383 C, and 384.5 C for B-MgZnO, L-MgZnO, and H-MgZnO layers, while keeping the Zn cell and substrate temperature at 310 C and 450 C. The in-plane epitaxial relationship is [11][12][13][14][15][16][17][18][19][20] MgZnO // [11][12][13][14][15][16][17][18][19][20] BeO // Si confirmed by reflection high-energy electron diffraction (RHEED) and transmission electron microscope (TEM). 17 More details of the epitaxial growth can be found elsewhere.…”

“…Until now, most of the Mg x Zn 1Àx O UV PDs have been constructed on insulating sapphire substrates with planar metal-semiconductor-metal (MSM) structures. 13,14 These PDs are not compatible with the mature Si micro-electronic technologies and thus unlikely to be applied in modern integrated circuits. There are some limited reports of Mg x Zn 1Àx O UV PDs fabricated on Si wafers with cutoff wavelengths in visible-blind region.…”

Band tail state related photoluminescence and photoresponse of ZnMgO solid solution nanostructured films

“…The ZnMgO solid solution system is of interest due to the possibility to tailor many important physical properties by varying their composition. This alloy system covers a wide ultraviolet (UV) spectral range between the direct bandgaps of 3.36 eV for ZnO and 7.8 eV for MgO at room temperature, making it very attractive for short-wavelength optical applications such as UV detectors [1][2][3][4][5] and light emitters [6][7][8][9].…”

“…Various techniques have been used for the preparation of ZnMgO films such as radio-frequency plasma-assisted molecu-lar beam epitaxy (RF-MBE) [2,7,10,11], DC [12,13] and RF [1,3,6] magnetron sputtering, pulsed laser deposition (PLD) [14,15], plasma-enhanced atomic layer deposition (PE-ALD) [16], chemical vapor deposition (CVD) [17], metal-organic chemical vapor deposition (MOCVD) [18,19], hydrothermal [4], chemical bath deposition (CBD) [20], sol-gel spin coating [21][22][23][24][25][26][27][28][29], and spray pyrolysis [28][29][30][31][32][33][34]. Among these techniques, the sol-gel spin coating method has the advantage of ensuring easy control and handling of chemicals and substrates, as well as excellent control over stoichiometry.…”

“…The films are prepared on various substrates such as ZnO [6], MgO [17], Si [2][3][4]23], CaF 2 [12], Al 2 O 3 [18], sapphire [7,10,11,[13][14][15][16]19,31,32], glass and quartz [1,20,21,[23][24][25][26][27][28][29][30]33,34]. The choice of the substrate is determined by the application.…”