In situ reflectance monitoring of overgrowth of InGaAs gratings in laser diode manufacture

Spectral reflectance measurements of InP overgrowth upon RIE prepared grati ngs provide for in situ measurements of layer thickness to control the coup ling constant (K) of the laser mode to the grating. We show that the use of a commercially available reflectometer utilized on a rotating disk reactor provides growth rate measurements of InP overgrowth of InGaAs gratings wit h 50% duty cycle as well as patterned gratings. Spectral reflectance (SR) d etermined thickness has been correlated to post-growth measurements such as cross section SEM and XRAY measurements with good results. SR measurements also provide an optical signature of grating overgrowth that has thermally degraded gratings and grating overgrowth that can lead to low photolumines cence of MQW layers. The results of these measurements are improved process control of grating overgrowth in laser diode manufacture, enabling higher yields. (C) 2000 Elsevier Science B.V. All rights reserved.