▁ 3 2 ▁% ▁and ▁can ▁operate ▁also ▁with ▁light ▁as ▁concentr ated ▁as ▁ 2 , 0 0 0 ▁sun s . ▁This ▁kind ▁of ▁solar ▁cell ▁power ed ▁the ▁Mars ▁Ex pl oration ▁Ro vers ▁Spirit ▁and ▁O pport unity , ▁which ▁expl ored ▁Mars ' ▁surface . ▁Also ▁many ▁solar ▁cars ▁util ize ▁Ga As ▁in ▁solar ▁arrays . ▁ ▁Ga As - based ▁devices ▁hold ▁the ▁world ▁record ▁for ▁the ▁highest - e ffic iency ▁single - j unction ▁solar ▁cell ▁at ▁ 2 9 . 1 ▁% ▁( as ▁of ▁ 2 0 1 9 ). ▁This ▁high ▁efficiency ▁is ▁attributed ▁to ▁the ▁extreme ▁high ▁quality ▁Ga As ▁ep it ax ial ▁growth , ▁surface ▁pass iv ation ▁by ▁the ▁Al G a As , ▁and ▁the ▁promotion ▁of ▁phot on ▁rec y cling ▁by ▁the ▁thin ▁film ▁design . ▁ ▁Complex ▁designs ▁of ▁Al x G a 1 − x As - G a As ▁devices ▁using ▁quantum ▁well s ▁can ▁be ▁sensitive ▁to ▁inf ra red ▁radiation ▁( Q W IP ). ▁ ▁Ga As ▁di odes ▁can ▁be ▁used ▁for ▁the ▁detection ▁of ▁X - ray s . ▁ ▁Light - em ission ▁devices ▁ ▁Ga As ▁has ▁been ▁used ▁to ▁produce ▁near - inf ra red ▁las er ▁di odes ▁since ▁ 1 9 6 2 . ▁ ▁F iber ▁opt ic ▁temperature ▁measurement ▁For ▁this ▁purpose ▁an ▁optical ▁fi ber ▁tip ▁of ▁an ▁optical ▁fi ber ▁temperature ▁sensor ▁is ▁equ ipped ▁with ▁a