Design considerations for InGaAlP lasers and light–emitting diodes on high–index GaAs substrates for the yellow and green spectral range

摘要

We consider the impact of strain and substrate orientation on the conduction band (CB) and valence band (VB) energiesin (Al,Ga,In)P materials. We show that applying tensile strained GaP–rich insertions as barriers in lattice–matchedheterostructures grown on high–index GaAs substrates, like (211), (322), and (111) ones, allows to overcome the mainproblem of (Al,Ga,In)P materials, namely the cross–over of the Γ and X minima of the CB in (In,Ga,Al)P alloy at ~55%AlInP content which hinders the possibility to extend the spectral range of the devices towards shorter wavelengths.Adding GaP–enriched insertion for structures grown on the (111) substrate allows to shift the X minimum upwardsforming a potential barrier for electrons escaping the active region. Both the initial energy of the CB X minimum of GaP,the highest among Ⅲ–Ⅴ binaries, and the tensile strain help. For other orientations the effect is reduced or is even ofopposite sign due to the splitting of the X band minimum upon applied strain. For high strain an impact on the Γ and Lminima in the barrier insertion are to be considered, as both minima are strongly shifted downwards once the strainedinsertion is parallel to the (111) plane. Admixture of AlP helps to push the Γ and L minima to higher energies (additional1 eV for L minimum for AlP compared to GaP) even at the expense of a smaller increase of the X band–induced barrier.Experimental results confirm the predictions, revealing lasing at 599 nm at room temperature. We show that with propersubstrate orientation and the composition of the strained barriers one can strongly modify and tune the CB minimaextending the spectral rage of InGaAlP lasers to wavelengths shorter than ～570–590 nm at room temperature.