Yu Chang Lin

Enhanced Performance of Mg0.1Zn0.9O UV Photodetectors Using Photoelectrochemical Treatment and Silica Nanospheres

The Mg0.1Zn0.9O films were grown using atomic layer deposition (ALD) system and applied to metal-semiconductor-metal ultraviolet photodetectors (MSM-UPDs) as an active layer. To suppress the dangling bonds on the Mg0.1Zn0.9O surface, the photoelectrochemical (PEC) treatment was used to passivate the Mg0.1Zn0.9O surface, which could reduce the dark current of the MSM-UPDs about one order. Beside, to increase more incident light into the Mg0.1Zn0.9O active layer of the MSM-UPDs, the 500-nm-diameter silica nanospheres were spin-coated on the Mg0.1Zn0.9O active layer to improve the antireflection capability at the wavelength of 340 nm. The reflectivity of the Mg0.1Zn0.9O films with silica nanospheres antireflection layer decreased about 7.0% in comparison with the Mg0.1Zn0.9O films without silica nanospheres. The photocurrent and UV-visible ratio of the passivated Mg0.1Zn0.9O MSM-UPDs with antireflection layer were enhanced to 5.85 μA and , respectively, at the bias voltage of 5 V. Moreover, the noise equivalent power and the specific detectivity of the passivated Mg0.1Zn0.9O MSM-UPDs with antireflection layer were decreased to  W and increased to  cmHz1/2W−1, respectively, at the bias voltage of 5 V. According to the above mentions, the PEC treatment and silica nanospheres antireflection layer could effectively enhance the performance of Mg0.1Zn0.9O MSM-UPDs.

Performance comparison of p-side-up thin-film AlGaInP light emitting diodes with aluminum-doped zinc oxide and indium tin oxide transparent conductive layers

Transparent conductive layers (TCLs) deposited on a GaP window layer were used to fabricate high-brightness p-side-up thin-film AlGaInP light-emitting diodes (LEDs) by the twice wafer-transfer technique. Indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO) were used as TCLs for comparison. The TCLs improved droop of external quantum efficiencies (EQE) of LEDs and junction temperature, which result in increasing the light output power and thermal stability of the LEDs. The droop efficiency of Ref-LED, ITO-LED and AZO-LED were 64%, 27% and 15%, respectively. The junction temperature of ITO-LED and AZO-LED reduced to 49.3 and 39.6 °C at an injection current of 700 mA compared with that (80.8 °C) of Ref-LED. The LEDs with AZO layers exhibited the most excellent LED performance. The emission wavelength shifts of LEDs without a TCL, with an ITO layer, and with an AZO layer were 17, 8, and 3 nm, respectively, when the injection current was increased from 20 to 1000 mA. The above results are promising for the development of AZO thin films to replace ITO thin films for AlGaInP LED applications.

Effect of hydrogen peroxide pretreatment on ZnO-based metal–semiconductor–metal ultraviolet photodetectors deposited using plasma-enhanced atomic layer deposition

In this study, zinc oxide (ZnO) films were deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system. Prior to deposition, the substrates were treated with hydrogen peroxide (H2O2) in order to increase nucleation on the initial sapphire surface and, thus, enhance the quality of deposited ZnO films. Furthermore, x-ray diffraction spectroscopy measurements indicated that the crystallinity of ZnO films was considerably enhanced by H2O2 pretreatment, with the strongest (002) diffraction peak occurring for the film pretreated with H2O2 for 60 min. X-ray photoelectron spectroscopy also was used, and the results indicated that a high number of Zn–O bonds was generated in ZnO films pretreated appropriately with H2O2. The ZnO film deposited on a sapphire substrate with H2O2 pretreatment for 60 min was applied to metal–semiconductor–metal ultraviolet photodetectors (MSM-UPDs) as an active layer. The fabricated ZnO MSM-UPDs showed improvements in dark current and ultraviolet–visible rej...

Performance improvement of GaN-based flip-chip white light-emitting diodes with diffused nanorod reflector and with ZnO nanorod antireflection layer

The GaN-based flip-chip white light-emitting diodes (FCWLEDs) with diffused ZnO nanorod reflector and with ZnO nanorod antireflection layer were fabricated. The ZnO nanorod array grown using an aqueous solution method was combined with Al metal to form the diffused ZnO nanorod reflector. It could avoid the blue light emitted out from the Mg-doped GaN layer of the FCWLEDs, which caused more blue light emitted out from the sapphire substrate to pump the phosphor. Moreover, the ZnO nanorod array was utilized as the antireflection layer of the FCWLEDs to reduce the total reflection loss. Thelight output power and the phosphor conversion efficiency of the FCWLEDs with diffused nanorod reflector and 250 nm long ZnO nanorod antireflection layerwere improved from 21.15mW to 23.90mW and from 77.6% to 80.1% in comparison with the FCWLEDs with diffused nanorod reflector and without ZnO nanorod antireflection layer, respectively

Enhanced light extraction in wafer-bonded p-side-up thin-film AlGaInP light emitting diodes via zinc oxide nanorods

ZnO nanorods grown via hydrothermal method on the aluminum-doped zinc oxide (AZO) thin film were used to fabricate high-brightness p-side-up thin-film AlGaInP light-emitting diodes (LEDs). The AZO thin film was not only used as current spreading layers but also as a seed layer of ZnO nanorods. The AZO thin film was prepared using atomic layer deposition. The ZnO nanorods improved light extraction, thus increasing the light output power of the LEDs. The output powers of LEDs with optimum ZnO nanorod structures were increased by 32% at an injection current of 700 mA, as compared with that of an LED with AZO thin film. The emission wavelength shifts of LEDs with an AZO thin film and optimum ZnO nanorod structure were 18 and 11 nm, respectively, when the injection current was increased from 20 to 1000 mA. The ZnO nanorods not only provide more light extraction but also keep the thermal stability of the LED device without any degradation. The results are promising for the developed high brightness AlGaInP LED applications with low fabrication cost through ZnO nanorods grown by hydrothermal method to enhance the light extraction efficiency.

Performance enhancement of MgZnO ultraviolet photodetectors using ultrathin Al2O3 inserted layer

In this study, the magnesium zinc oxide (MgZnO) films and ultrathin alumina (Al2O3) inserted layers were subsequently deposited on sapphire substrates using a plasma-enhanced atomic layer deposition system, and applied in metal-semiconductor-metal ultraviolet (UV) photodetectors (MSM-UPDs). The dark current of the MgZnO MSM-UPDs was decreased from 1 to 0.34 nA with an increase in Al2O3 layer thickness from 0 to 5 nm. The ultrathin Al2O3 inserted layer effectively passivated the dangling bonds on the MgZnO surface and blocked leakage current. At a bias voltage of 5 V, the maximum UV-visible rejection ratio of the MgZnO MSM-UPDs was 1.78 × 103 with 5-nm-thick Al2O3 inserted layer. Furthermore, the noise equivalent power and detectivity of MgZnO MSM-UPDs with 5-nm-thick Al2O3 inserted layer were improved from 1.26 × 10−14 W and 2.50 × 1013 cm Hz1/2 W−1 to 0.93 × 10−14 W and 3.40 × 1013 cm Hz1/2 W−1 in comparison with MgZnO MSM-UPDs without Al2O3 inserted layer. The high performances of MgZnO MSM-UPDs were ac...

Study of Aluminum-doped zinc oxide current spreading layer on P-side up thin-film AlGaInP-based light-emitting diodes by ALD

A twice wafer-transfer technique can be used to fabricate high-brightness p-side-up thin-film AlGaInP-based light-emitting diodes (LEDs) with an aluminum-doped zinc oxide (AZO) thin films transparent conductive layer deposited on a GaP window layer. The GaP window layer consist of the two different doping profile, the carbon doped Gap (GaP:C) window layer of 50 nm is on the top of Mg doped GaP window layer of 8 μm. The GaP:C window layer is used to improved the ohmic contact properties of GaP:C/AZO. The AZO with different cycle ratio of Zn:Al (15:1, 20:1 and 25:1) is deposited on GaP:C window layer as current spreading layer by atomic layer deposition. The AZO layer can be used to improve light extraction, which enhances light output power. The output power of p-side-up thin-film AlGaInP LED with an AZO layer of 20:1 cycle ratio has improved up to 19.2 % at injection current of 350 mA, as compared with that of LED without AZO film. The p-side-up thin-film AlGaInP LED with AZO current spreading layer exhibited excellent performance stability, the emission wavelength shift of p-side-up thin-film AlGaInP LED without and with AZO thin film(Zn:Al=20:1) are 17 nm and 3 nm under the injection current increased from 20 mA to 1000mA, respectively. This stability can be attributed to the following factors: 1) Refractive index matching, performed by introducing AZO thin film between the epoxy and the GaP window layer enhances light extraction; and 2) the favorable thermal dissipation of the silicon substrate reduces thermal degradation.