The frequency-tripled neodymium-doped yttrium aluminum garnet laser <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mn>355</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>nm</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>(355nm) and the KrF pulsed excimer laser <mml:math display="inline"><mml:mrow><mml:mo>(</mml:mo><mml:mn>248</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>nm</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>(248nm) were employed to separate GaN thin films from sapphire substrates and to transfer the films to bond with other substrates. The different laser lift-off processes would generate the dislocation density on different regions. In this study, the effects of these two laser sources on structural damage mechanisms and reverse-bias leakages of InGaN–GaN light-emitting diodes (LEDs) were studied.

Cu direct bonding has been achieved at 150 °C by using (111)-oriented nanotwinned Cu (nt-Cu) because it has the fastest surface diffusivity. In this study, nt-Cu was bonded at even lower temperature of 120 °C by roughening one of the nt-Cu surfaces. However, the flat-to-flat nt-Cu could not be bonded at the same temperature. This result violates a bonding concept that “for good wafer bonding, the contact area must be as large as possible”. This paper discusses in detail two possible bonding mechanisms: diffusion and creep/plastic deformation.

Non-radiative energy transfer (NRET) from quantum dots (QDs) to monolayer MoS₂ has been shown to greatly enhance the photoresponsivity of the MoS₂ photodetector, lifting the limitations imposed by monolayer absorption thickness. Studies were often performed on a photodetector with a channel length of only a few μm and an active area of a few μm². Here, we demonstrate a QD sensitized monolayer MoS₂ photodetector with a large channel length of 40 μm and an active area of 0.13 mm². The QD sensitizing coating greatly enhances photoresponsivity by 14-fold at 1.3 μW illumination power, as compared with a plain monolayer MoS₂ photodetector without QD coating. The photoresponsivity enhancement increases as QD coating density increases. However, QD coating also causes dark current to increase due to charge doping from QD on MoS₂. At low QD density, the increase of photocurrent is much larger than the increase of dark current, resulting in a significant enhancement of the signal on/off ratio. As QD density increases, the increase of photocurrent becomes slower than the increase of dark current. As a result, photoresponsivity increases, but the on/off ratio decreases. This inverse dependence on QD density is an important factor to consider in the QD sensitized photodetector design.