Determination of carrier lifetime and diffusion length in Al-doped 4H-SiC epilayers by time-resolved optical techniques

被引:15
作者
Liaugaudas, Gediminas [1 ]
Dargis, Donatas [2 ]
Kwasnicki, Pawel [3 ]
Arvinte, Roxana [4 ]
Zielinski, Marcin [4 ]
Jarasiunas, Kestutis [1 ,2 ]
机构
[1] Vilnius Univ, Dept Semicond Phys, LT-10222 Vilnius, Lithuania
[2] Vilnius Univ, Inst Appl Res, Dept Semicond Optoelect, LT-10222 Vilnius, Lithuania
[3] Univ Montpellier 2, CNRS, UMR 5221, Lab Charles Coulomb L2C, Montpellier, France
[4] NOVASiC, F-73375 Le Bourget Du Lac, France
关键词
carrier lifetime; diffusion length; Al-doped; 4H-SiC; time-resolved optical techniques; DENSITY; DEPENDENCE; TRANSPORT; FILMS;
D O I
10.1088/0022-3727/48/2/025103
中图分类号
O59 [应用物理学];
学科分类号
摘要
A series of p-type 4H-SiC epilayers with aluminium concentration ranging from 2 x 10(16) to 8 x 10(19) cm(-3) were investigated by time-resolved optical techniques in order to determine the effect of aluminium doping on high-injection carrier lifetime at room temperature and the diffusion coefficient at different injections (from approximate to 3 x 10(18) to approximate to 5 x 10(19) cm(-3)) and temperatures (from 78 to 730 K). We find that the defect limited carrier lifetime tau(SRH) decreases from 20 ns in the low-doped samples down to approximate to 0.6 ns in the heavily doped epilayers. Accordingly, the ambipolar diffusion coefficient decreases from D-a = 3.5 cm(2) s(-1) down to approximate to 0.6 cm(2) s(-1), corresponding to the hole mobility of mu h = 70 cm(2) Vs(-1) and 12 cm(2) Vs(-1), respectively. In the highly doped epilayers, the injection-induced decrease of the diffusion coefficient, due to the transition from the minority carrier diffusion to the ambipolar diffusion, provided the electron diffusion coefficient of De approximate to 3 cm(2) s(-1). The Al-doping resulted in the gradual decrease of the ambipolar diffusion length, from L-D = 2.7 mu m down to L-D = 0.25 mu m in the epilayers with the lowest and highest aluminium concentrations.
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页数:7
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