β-Ga_2O_3 and single-crystal phosphors for high-brightness white LEDs LDs, and β-Ga_2O_3 potential for next generation of power devices

摘要

β-Ga_2O_3 is the most transparent conductive oxide, well known since several decades for its large bandgap of 4.8 eV. Its potential as semiconductor material, however, is just emerging in recent years. Present work shows the development of β-Ga_2O_3 for semiconductor applications and its current state-of-the-art. The discussion is focused on three different aspects: (1) Advantageous growth from melt of large-size β-Ga_2O_3 single-crystals. High-crystalline quality and carrier control make possible the production of conductive and semi-insulating wafers. (2) β-Ga_2O_3 as substrate for homoepitaxy as well as for heteroepitaxial deposition of GaN-based devices. High-brightness blue-LEDs with vertical current injection are demonstrated. (3) Potential of β-Ga_2O_3 for high-power devices with higher breakdown voltage than GaN and SiC counterparts. The first Schottky barrier diode is shown, as well as first transistors (MESFET and MOSFET) are indicated. Single-crystal phosphors are introduced as novel alternative to currently used powder phosphors. In connection with high-brightness white light-sources, based on LEDs or LDs plus phosphor converters, single-crystal phosphors possess advantageous features. These avoid the use of resins and exhibit a very high internal quantum efficiency, which remains stable with the temperature increase.