Semiconductor laser structure for improved stability of the threshold current with respect to changes in the ambient temperature

A semiconductor lasing device having an active region comprising a first heterojunction structure with a nested bandgap alignment and a second heterojunction structure having a virtual, staggered bandgap alignment, said second heterojunction structure comprising:

• first, second and third regions of semiconductor material with said second region said first and third regions;
• the material of said first region having a conduction energy level valance band with an energy level V.sub.1 defining therebetween a first bandgap E.sub.1 ;
• the material of said second region having a conduction band with an effective energy level C.sub.2 and a valance band with an effective energy level V.sub.2 defining therebetween a second effective bandgap E.sub.2 and;
• the material of said third region having a conduction band with an energy level C.sub.3 and a valance band with an energy level V.sub.3 defining therebetween a third bandgap E.sub.3 ;
• wherein
• E.sub.3 >E.sub.2 ;
• E.sub.3 >E.sub.1 ;
• C.sub.1 <C.sub.2 <C.sub.3 ;
• and
• V.sub.3 <V.sub.1 <V.sub.2.