The band offset occuring at an abrupt hetero-interface in heterojunction materials and the carrier confinement behaviour at this interface have been studied for many years. A new photoluminescence (PL) spectrum

H-line

has been observed from the undoped or lightly doped GaAs/AlGaAs hetero-junction grown by LPE.The luminescence of H-line was shown between exciton and acceptor related transitions at low temperature

with peak energy ranging from that of the bound exciton to that of the shallowest acceptor transitions

increasing with the excitation intensity. Also

it dependents on the experiment temperature and the composition of heterojunction materials. The H-line can be considered to originate from the GaAs/AlGaAs interface. A few researches about the H-line and related behaviour have been done on MBE growth GaAs/AlGaAs heterojunctions. The purpose of this paper is to describe the X-ray diffraction and pico-second(ps)PL results about the H-line transition. A model of two dimensional exciton effect has been used successfully to explain the H-line experimental results.LPE GaAs/AlGaAs samples with similar heterojunction structure Were used to study the relation between H-line and the crystal quality. Double crystal X-ray rocking curves of (400)

(511) and (322) diffractive directions and reflective topography of hetero-structure crystal were taken by a Rigakn CN 1518B1 scanning X-ray double crystal aiffractor. In the sample whose H-line can be observed

the half width of rocking curve is sharp

and the topography shows uniform stress distribntion and less deffects.The H-line would be missing in that samples with more deffects and ununiform stress distribution. It can be confirmed that the H-line comes from good heterojunction qnality with perfect interface.