Development of high efficient green LEDs of ZnSSe:Te-ZnMgSSe DH structure on p-GaAs and its degradation mechanism

We present new green double‐hetero (DH) structure light‐emitting diodes (LEDs) of ZnSSe:Te (active layer)–ZnMgSSe (cladding layer) on p‐type GaAs substrates grown by molecular beam epitaxy (MBE).We have confirmed very efficient green emission in Te‐bias modulation doped ZnSSe:Te consists of ZnSSe:Te (Te: 2%, 50 Å)/ZnSSe:Te (Te: 5%, 50 Å) superlattice. A LED with this modulation doping also shows a strong durability for device degradation due to effective Te‐hardening effect. A new LED structure on ptype GaAs exhibits a high extraction efficiency of light emission, which is three times larger in magnitude than LEDs on n‐type GaAs. The new LED also reveals a long device lifetime (in bare chip) over 1300 hours under 3A/cm2 at room temperature. From a simple aging test on the green LEDs, gradual degradation is classified into “slow‐mode degradation”, which is caused by a generation of point defects (donor‐like centers) in p‐type ZnMgSSe cladding layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)